Releasing the Truth

Digging for knowledge…

Tag Archives: RNA

Abiogenesis enigma: Protein’s origin

Proteins

As you might know, proteins are one of the major “building blocks” of cells; there’s up to 10.000 different types of proteins, all manufactured inside each cell. Abiogenesis theorists  obviously supports the view that these molecules have arisen “by chance”, in a prebiotic world, billion years ago, however, to date, they have absolutely no clue about it, as we can read from this article:

“Proteins are the most complex chemicals synthesized in nature and must fold into complicated three-dimensional structures to become active. This poses a particular challenge in explaining their evolution from non-living matter. So far, efforts to understand protein evolution have focused on domains, independently folding units from which modern proteins are formed. Domains however are themselves too complex to have evolved de novo in an abiotic environment. We think that domains arose from the fusion of shorter, non-folding peptides, which evolved as cofactors supporting a primitive, RNA-based life form (the ‘RNA world’).” 1

So, why is it so complicated to explain its origin? Despite the often repeated innuendo that life and all of its components has “assuredly” originated through natural means, the clear failure of scientists to solve this puzzle can be easily explained by some truths about proteins, its synthesis, structure and so on. After that, no one can reasonably take its abiogenetic origin as logically granted. These truths also explain without shadow of doubt the intriguing fact that absolutely no single protein (even the lesser one, composed of only 8 amino acids) has ever been observed to appear anywhere in the world, outside the cells and high-tech labs, of course!

What’s a protein?

“Proteins are large biological molecules consisting of one or more chains of amino acids. Proteins perform a vast array of functions within living organisms, including catalyzing metabolic reactionsreplicating DNAresponding to stimuli, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in folding of the protein into a specific three-dimensional structure that determines its activity.

A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the genetic code specifies 20 standard amino acids;” 2

Talking about amino acids, we’d like to recall another crucial problem for abiogenesis: The absence of self-occurring homochiral mixtures. As it has been told in a previous article, the laws of thermodynamics obliges the occurrence of racemic mixtures, ever:

“The left and right handed forms have identical free energy (G), so the free energy difference (ΔG) is zero. The equilibrium constant for any reaction (K) is the equilibrium ratio of the concentration of products to reactants. The relationship between these quantities at any Kelvin temperature (T) is given by the standard equation:

K = exp (–ΔG/RT)

where R is the universal gas constant (= Avogadro’s number x Boltzmann’s constant k) = 8.314 J/K.mol.

For the reaction of changing left-handed to right-handed amino acids (L → R), or the reverse (R → L), ΔG = 0, so K = 1. That is, the reaction reaches equilibrium when the concentrations of R and L are equal; that is, a racemate is produced.”

Therefore, any abiogenetic theorist has this astounding problem to deal with from the very beginning; without homochiral monomers, we can have zero possibility of a ‘magic’ protein self-assembling…

 

Protein synthesis

 

It’s quite uncanny that intelligent people with advanced knowledge on the subject might attempt to conceive hypothesis of such molecules originating spontaneously, in the wild and morbid inorganic environment, because for cells to build proteins, an intricate, complex and laborious process must take place!

 

 

First, genetic information is needed:

“Proteins are assembled from amino acids using information encoded in genes. Each protein has its own unique amino acid sequence that is specified by the nucleotide sequence of the gene encoding this protein. The genetic code is a set of three-nucleotide sets called codons and each three-nucleotide combination designates an amino acid (for example AUG (adenineuracilguanine) is the code for methionine).”

 

Many proteins use more that one of the 64 possible codons to be built. Moreover, that specific genetic code must be first translated, transcribed:

“Genes encoded in DNA are first transcribed into pre-messenger RNA (mRNA) by proteins such as RNA polymerase. Most organisms then process the pre-mRNA (also known as a primary transcript) using various forms of Post-transcriptional modification to form the mature mRNA, which is then used as a template for protein synthesis by the ribosome.”

Oh great, a bit complicated, isn’t it? Please, read the Wikipedia article referring to the messenger RNA, for further comprehension of what it is, its manufacturing, composition, etc; all of which adds up more complexity for the protein origin’s explanation.

 

 

The process of synthesizing a protein from an mRNA template is known as translation. The mRNA is loaded onto the ribosome and is read three nucleotides at a time by matching each codon to its base pairing anticodon located on a transfer RNA molecule, which carries the amino acid corresponding to the codon it recognizes. The enzyme aminoacyl tRNA synthetase “charges” the tRNA molecules with the correct amino acids. The growing polypeptide is often termed the nascent chain. Proteins are always biosynthesized from N-terminus to C-terminus.[6]

The size of a synthesized protein can be measured by the number of amino acids it contains and by its total molecular mass, which is normally reported in units of daltons (synonymous with atomic mass units), or the derivative unit kilodalton (kDa). Yeast proteins are on average 466 amino acids long and 53 kDa in mass.[5] The largest known proteins are the titins, a component of the muscle sarcomere, with a molecular mass of almost 3,000 kDa and a total length of almost 27,000 amino acids.[8]

 

Phew! How complicated! You may ask now: are we finally done? And I reply you: Huh, nope! Now that the ribosome, together with the rRNA and more than 50 other proteins, has finally finished the process, a protein is formed. However, it is always found in a  random coil shape. So what? This shape is mostly useless for its usage on organism, as we can read:

Each protein exists as an unfolded polypeptide or random coil when translated from a sequence of mRNA to a linear chain of amino acids. This polypeptide lacks any stable (long-lasting) three-dimensional structure (the left hand side of the neighbouring figure). 3

In that randomly coiled shape, the protein is highly unstable, breakable, useless for cell building, so, for proper biological use and better stability, the protein folding process must take place. This 3D-shape is known as the native state.

The correct three-dimensional structure is essential to function, although some parts of functional proteins may remain unfolded.[4] Failure to fold into native structure generally produces inactive proteins, but in some instances misfolded proteins have modified or toxic functionality. Several neurodegenerative and other diseases are believed to result from the accumulation of amyloid fibrils formed by misfolded proteins.[5] Many allergies are caused by incorrect folding of some proteins, for the immune system does not produce antibodies for certain protein structures.[6]

Another importance of the protein folding is:

 

Minimizing the number of hydrophobic side-chains exposed to water is an important driving force behind the folding process.[9] Formation of intramolecular hydrogen bonds provides another important contribution to protein stability.[10] 

 

And how does the folding occurs?

 

 

The amino-acid sequence of a protein determines its native conformation.[7] A protein molecule folds spontaneously during or after biosynthesis. While these macromolecules may be regarded as “folding themselves“, the process also depends on the solvent (water or lipid bilayer),[8] the concentration of salts, the pH, the temperature, the possible presence of cofactors and of molecular chaperones.

The process of folding often begins co-translationally, so that the N-terminus of the protein begins to fold while the C-terminal portion of the protein is still beingsynthesized by the ribosome. Specialized proteins called chaperones assist in the folding of other proteins.

Although most globular proteins are able to assume their native state unassisted, chaperone-assisted folding is often necessary in the crowded intracellular environment to prevent aggregation; chaperones are also used to prevent misfolding and aggregation that may occur as a consequence of exposure to heat or other changes in the cellular environment.

There are two models of protein folding that are currently being confirmed: The first: The diffusion collision model, in which a nucleus is formed, then the secondary structure is formed, and finally these secondary structures are collided together and pack tightly together. The second: The nucleation-condensation model, in which the secondary and tertiary structures of the protein are made at the same time. Recent studies have shown that some proteins show characteristics of both of these folding models.

The essential fact of folding, however, remains that the amino acid sequence of each protein contains the information that specifies both the native structure and the pathway to attain that state. Folding is a spontaneous process independent of energy inputs from nucleoside triphosphates. The passage of the folded state is mainly guided by hydrophobic interactions, formation of intramolecular hydrogen bonds, and van der Waals forces, and it is opposed by conformational entropy.

Only after the folding process, we have an useful, stable protein, with a properly designed shape with its up to four layers, so that the molecule can perform its biological function.

But, remember, many conditions and external factors can destroy proteins, such as hydrolysis (it’s a slow, but ceaseless process, because proteins are metastable, hydrophobic) and others:

Under some conditions proteins will not fold into their biochemically functional forms. Temperatures above or below the range that cells tend to live in will cause thermally unstableproteins to unfold or “denature” (this is why boiling makes an egg white turn opaque). High concentrations of solutes, extremes of pH, mechanical forces, and the presence of chemical denaturants can do the same.

A fully denatured protein lacks both tertiary and secondary structurel. Under certain conditions some proteins can refold; however, in many cases, denaturation is irreversible.[15] Cells sometimes protect their proteins against the denaturing influence of heat with enzymes known as chaperones or heat shock proteins, which assist other proteins both in folding and in remaining folded. Some proteins never fold in cells at all except with the assistance of chaperone molecules, which either isolate individual proteins so that their folding is not interrupted by interactions with other proteins or help to unfold misfolded proteins, giving them a second chance to refold properly. This function is crucial to prevent the risk of precipitation into insoluble amorphous aggregates.

 

For a further an in-depth study about different factors capable of disrupting proteins, read the following articles:

https://en.wikipedia.org/wiki/Protein_biosynthesis

http://creation.com/native-folds-in-polypeptide-chains-1 (a series of 6 parts)

 

To conclude our observation, it’s impossible not to be sceptic of any theoretic proposition that claims self-caused origin of proteins, because it turns out that science unveiled tons of facts that easily prevent any possibility of such proposed scenario:

 

-Absence of homochiral monomers forming in the environment;

-Necessity of genetic specific information;

-Need for an highly controlled ambient, with proper Ph level, temperature, absence of mechanical forces that may easily damage, disrupt the protein, toxins, etc; 

-Need for specific methods to protect the protein against hydrolysis, oxidation;

-Necessity of having 50 other types of protein already manufactured to help on the protein synthesis;

 

The question raises: how in the world could such a specific set of conditions be found in a prebiotic Earth? Such condition can only be barely found in a first-class laboratory, driven by qualified and experienced scientists!

You might as well enjoy watching this short video talking about protein synthesis:

 

References

1. <http://www.eb.tuebingen.mpg.de/research/departments/protein-evolution/protein-evolution.html>

2. <https://en.wikipedia.org/wiki/Protein>

3. <https://en.wikipedia.org/wiki/Protein_folding>

DNA- fascinante obra de engenharia

Ácido desoxírribonucleico (DNA) é uma molécula que codifica as instruções genéticas usadas no desenvolvimento e funcionamento de todos os organismos vivos e inúmeros vírus. Junto com o RNA e as proteínas, o DNA é uma das três maiores macromoléculas essenciais para todas as formas vivas. A maioria das moléculas de DNA encontram-se na forma de dupla hélice, consistindo de dois longos biopolímeros de unidades simples chamadas nucleotídeos cada nucleotídeo é composto de uma nucleobase (base nitrogenada)(guanina, adenina, timina e citosina, mencionadas pelas respectivas siglas G,A,T e C), assim como por uma estrutura principal feita de açúcares alternantes (desoxirribose) e grupos fosfato (relacionado ao ácido fosfórico), com as nucleobased ligadas aos açúcares. DNA é feito sob medida para armazenamento de informação biológica, pois sua estrutura é resistente a rupturas e a estrutura em cadeia dupla providencia uma duplicação, cópia de segurança da informação genética. O seguinte vídeo (em inglês) demonstra alguns processos que ocorrem rotineiramente no DNA, dentro de cada uma de nossas 10 trilhões de células corporais, como o “empacotamento” do DNA antes da mitose (divisão celular), a duplicação das cadeias de DNA, transcrição deste por parte do RNA e a produção de novas proteínas.

Descoberta

Em 1927 Nikolai Koltsov propôs que os traços hereditários poderiam ser herdados através de uma “molécula hereditária gigante” feitas de “duas cadeias espelhadas que se replicariam em uma maneira semi-conservativa usando cada cadeia como gabarito”. Em 1928, Frederick Griffith descobriu que traços da forma “polida” do Pneumococcus poderia ser tranferida para a forma “grosseira” da mesma bactéria ao misturar bactéria morta “polida” com a forma via “grosseira”. Este sistema proveu-nos com a primeira clara sugestão de que o DNA carregaria informação genética O experimento de Avery— MacLeod— e MacCarty— Quando Oswald Avery, junto com os cooperadores Colin MacLeod e Maclyn MacCarty, indentificaram o DNA como o príncipio transformador em 1943. O papel do DNA na hereditariedade fora confirmado em 1952, quando Alfred Hershey e Martha Chase em seu famoso experimento demonstraram que o DNA é o material genético do fago T2.

Em 1953, James Watson e Francis Crick sugeriram o que é agora aceito como o primeiro modelo correto em dupla hélice da estrutura do ADN no jornal Nature. Seu modelo fora baseado em uma imagem de difração de raio-X (apelidado de “foto 51”) tirada por Rosalind Franklin e Raymond Gosling em Maio de 1952. Evidências experimentais corroborando o modelo de Watson e Crick foram publicadas em uma série de cinco artigos na Nature.

Sistema reparatório

Vale a pena notar que a molécula de DNA foi observada ser altamente reativa, portanto, muito instável, segundo recentes estudos. EM um dia comum cerca de um milhão de bases no DNA de uma única célula humana são danificados! Essas lesões são causadas pela combinação da atividade química corriqueira e exposição a radiação e toxinas advindas do nosso ambiente incluindo fumaça de cigarros, alimento grelhado e resíduos industriais. Portanto é essencial que os organismos possuam uma gama de sistemas reparatórios, como relatado em um recente artigo do Science Daily:

Uma série de toxinas ambientais e drogas quimioterápicas são agentes de alquilação que podem atacar o DNA. Quando uma base DNA se torna alquilada, forma-se então uma lesão que distorce a forma da molécula o suficiente para impedir a replicação bem-sucedida desta. Se a lesão ocorrer dentro de um gene, o mesmo pode deixar de funcionar. Para piorar a situação, existem dezenas de diferentes tipos de bases DNA alquiladas, cada um dos quais tem um efeito diferente sobre a replicação.

Um método de reparação dos danos que todos os organismos evoluíram é chamado de reparo por excisão de base. No BER, enzimas especiais conhecidas como DNA glicosilases viajam até a molécula de DNA escaneando em busca dessas lesões. Quando se deparam com uma, eles quebram a ligação de pares de base e invertem a base deformada. A enzima contém uma “bolsa” em formato especial que mantém a base deformada no lugar enquanto desmonta a “espinha dorsal” dela sem danificá-la. Isto deixa uma lacuna (denominada “zona abásica”) em que o DNA é reparado por um outro conjunto de enzimas.

O DNA humano possui uma única glicosilase nomeada de AAG, que repara bases alquiladas. Esta é especializada em detectar e deletar bases “etenoadeninas”, que foram deformadas pela combinação de lípidios altamente reativos, oxidantes, encontrados pelo corpo. Porém, AAG também lida com outras formas de danos alquilantes. Muitas bactériam, no entanto, possuem inúmeras variedades de glicosilases que lidam com variados tipos de danos.

É difícil de imaginar como glicosilases reconhecem diferentes tipos de danos alquilantes ao se estudar AAG pois ela reconhece inúmeros desses.” disse Eichman. “Então nós temos estudado glicosilases bacterianas afim de conseguir informações adicionais sobre o processo de detecção e reparo.”

Foi assim que eles descobriram a glicosilase bacteriana AlkD com seu esquema de detecção e reparo únicos. Todas glicosilases conhecidas funcionam basicamente assim: eles invertem a base deformada e mantém ela numa bolsa especial enquanto a recortam. AlkD, em contraposição, forçam ambas as bases deformadas e seu par a se virarem para o lado exterior da dupla hélice. Isso parece funcionar porque porque a enzima somente opera em bases deformadas que tenham adquirido uma excessiva carga positiva, tornando-as muito instáveis. Se deixadas assim, as bases deformadas irão se desprender espontaneamente. Todavia AlkD acelera o processo em até 100 vezes! Eichman especula se a enzima pode também permanecer no local e atrair enzimas reparadoras adicionais até lá.

AlkD tem uma estrutura molecular consideravelmente diferente de outras enzimas ou proteínas que se ligam ao DNA. No entanto, sua estrutura parece ser similar ao de outra classe de enzimas chamadas de quinases dependentes de DNA. Estas são moléculas enormes que possuem uma região ativa menor que tem um papel na regulação de de células que lidam com danos no DNA, Estruturas similares foram encontradas na porção das quinases com funções desconhecidas, leantando a possibilidade de que tenham um papel adicional ainda não reconhecido no reparo do ADN.”

O perigo dos raios UV

Tendo em vista a necessidade de inúmeros métodos de reparação e manutenção, é improvável imaginar que uma molecula instável e complexíssima como esta (cujas funções completas ainda estão para ser descobertas) possa ter surgido por si só, por acado, e possa ter durado tempo bastante em um meio ambiente pré-biótico. Numa Terra primordial, com atmosfera livre de O², não haveria camada de ozônio, ou haveria uma bem fina. Com isso, os raio UV nocivos do Sol poderiam bombardear a Terra em toda sua força, sem qualquer barreira, incluindo os piores tipos de raios UV. E, é fato que luz ultravioleta danifica, degrada polímeros! Esse problema conhecido como degradação UV é um problema comum, pois estraga muitos materiais feitos de polímeros sintéticos como nylon, polipropileno, etc. E este é somente um dos muitos problemas enfrentados por teorias proponentes de origens naturais dos seres vivos!

Corda de polipropileno estragada por raios UV ao lado de uma nova

 

Curiosidades:

-Um só DNA equivale a 3 GB de puro código (ou 200 listas telefônicas de Manhatan/NY de 1000 páginas);

-Desenrolada, uma molécula de DNA tem quase dois metros de comprimento, mas é muitas vezes mais fina que um fio de cabelo;

-Se desenrolassemos e emendassemos o DNA de cada célula de nossos corpos um ao outro, seu comprimento total daria para ir e voltar da Lua 600 vezes;

-Uma molécula de DNA é 4.5×10¹³ (45 trilhões) de vezes mais eficiente do que um moderno chip de silicone usados em computadores modernos;

 

Water and origin of life

 

Although water is portrayed by many as the solution to, or star player in how life came to be, the fact is that water spontaneously breaks down complex molecules that living organisms need to exist: such as DNA,* RNA, proteins and their components.**   For example, an article on Molecular Cloning says that  “Proteins are usually soluble in water solutions because they have hydrophilic amino acids on their surfaces.”1

 

Amino acids have been called the building blocks of life, and when two or more are joined together they are called a peptide and the bond that holds them together is called a peptide bond.  When ten or more are linked together they may be called a polypeptide, and if they are ordered and folded correctly, they become a protein.  And in a wikipedia article on peptide bonds we are told that a peptide bond can be broken by … hydrolysis” ***  (just by) … “adding … water” … (and that the) “… bonds in proteins are metastable, meaning that in the presence of water they will break spontaneously.” 2

 

A simple video explain dehydratation and hydrolysis:

 

Another article on this topic 3  says that hydrolysis is:

 

“A chemical reaction in which water is used to break the bonds of certain substances. In biotechnology and living organisms, these substances are often polymers … such as that … (exist) between two amino acids in a protein … “

 

Dr. A. E. Wilder-Smith, (Ph.D. organic chemistry) also brought this out in a book he wrote on life’s complexity and origin.4

 

“Amino acids and other building blocks present in the macromolecules of living matter aggregate to form larger units … by … (a reaction) called condensation.****  The combinations usually involve the elimination of one molecule of  water between two combining molecules.  It is the removal of this molecule of water which presents the major difficulty  …  For, the removal of this water molecule from between two combining molecules requires energy which must … be supplied in some fashion.

“A further difficulty arises in this question of the elimination of water.  For, in the prebiotic world, it is assumed that the condensation reaction took place in the presence of a large … (supply) of water which would tend, according to the law of mass action, to hinder the condensation process and … (promote)decomposition (or breakdown of peptides and polypeptides). … The more water, the less condensation.”

 

“If the reaction is to proceed in the direction of the dipeptide, (or two amino acids that are joined together) … the water molecule … (that results) must be removed from the reaction system since the reaction is reversible.  If it is not removed … (it will) hydrolyze (or separate) the dipeptide back again to the constituent amino acids …”

 

This means the “primordial soup,” or “warm little pond”  where Darwin speculated that life began could not have been simply water, since it would “hydrolyze” or break down complex molecules back into their basic original amino acid as soon as they formed.  Dr. Charles McCombs explains the problem as follows in an article he wrote on the subject of why life by chance  is virtually, if not utterly and completely impossible.  

 

“Every time one component reacts with a second component forming the polymer, the chemical reaction also forms water as a byproduct …  There is a rule of chemical reactions … called the Law of Mass Action that says all reactions proceed in a direction from highest to lowest concentration. This means that any reaction that produces water cannot be performed in the presence of water. This Law of Mass Action provides a total hindrance to protein, DNA/RNA, and polysaccharide formation because even if the condensation took place, the water from a supposed primordial soup would immediately hydrolyze them. Thus, if they are formed according to evolutionary theory, the water would have to be removed … which is impossible in a “watery” soup.5

 

But because the “watery soup” in living cells is surrounded by a membrane, the “water” inside the cell “behaves very differently” 6  than ordinary water.  In fact, the “water” in a cell is not water but a blend of water, amino acids, proteins, and many other chemicals called cytosol. This mixture is the result of the DNA’s ability to regulate what goes in and out of the cell — via  numerous channels that control and regulate what is allowed to pass through the cell membrane, and thus to create and maintain a favorable environment and PH for DNA, RNA and protein synthesis, and life itself to exist. 

If the concentration of amino acids is high enough, some of them will link up with others to form dipeptides and tripeptides.  An article on this subject states that:

“is important to recognize that by whatever reactions polymerization (or the joining of amino acids)occurred, they had to be reactions that would occur in an essentially aqueous environment. This presents difficulties because condensation of amino acids to form peptides, or of nucleotides to form RNA or DNA, is not thermodynamically favorable in aqueous solution.”{6}

The explanation for this is partly that the concentration of amino acids decreases as amino acids form pairs (called dipeptides) in a solution. This decreased concentration causes the velocity of the peptide synthesis reaction to slow down, and some dipeptides begin breaking up, again becoming single amino acids. The solution reaches equilibrium when just as many dipeptides dissociate as associate. A very tiny fraction of the dipeptides add another amino acid to form a tripeptide. … Oligopeptides (Oligo=few) and polypeptides (poly=many) will form only very rarely. Tripeptides dissociate faster than dipeptides in the same solution. 7

In this regard, a tripeptide has only three amino acids, while the simplest protein ever found has at least eight: connected in a specific order.

Jeffrey P. Tomkins makes the following statement in a book on the design and complexity of the cell:

 

“… plasma membranes are … quite complex and … (function) as more than just a barrier … Some key functions  of the membrane involve the import and export of chemical compounds through specialized transmembrane channels, sensory and signaling processes via specialized receptor proteins imbedded in the membrane, and osmotic (water) regulation … through special portals.” 8

“Within the … membrane is the internal cell matrix … called cytosol or cytoplasm, which is a semi-fluid substance.  …  Like the … membrane, the complexity of … cytoplasm seems to grow with every new discovery in cell biology.” 8

 

Tomkins also tells us that water must be regulated and controlled outside the cell as well in what is called the “extra cellular matrix.”  

This means that the water of yesteryear, or the distant past, almost certainly performed just like the water of today, and that water, dirt and chemicals, could not have created life anymore than fuel, dirt, and metallic ore, — by themselves — could create a car, motorcycle, or an  airplane: even in millions, billions, or trillions of years.  

 

 

A typical human cell would undergo 2,000 to 10,000 spontaneous DNA hydrolysis damage events every day just because it is an aqueous environment.(The only reason that DNA functions as well as it does is that cells come equipped with an amazing array of cooperative DNA repair mechanisms. For example, polymerase replication during cell division might produce 6 million errors per cell, but then proofreading machinery can reduce this to 10,000 and then mis-match repair machinery could reduce this to 100. It appears to be impossible, however, to replicate the 6 billion nucleotides in a human cell in a completely error-free manner.

A way to remove water is with certain high-energy chemicals that absorb water, called condensing agents. If the reaction between condensing agent C and water is:

C + H2O → D (2)

and if ΔG2 of reaction (2) is negative and large enough, it can couple with reaction (1):

H2NCHRCOOH + H2NCHR′COOH + C → H2NCHRCONHCHR′COOH + D (3)

ΔG3 = ΔG1 + ΔG2. If ΔG3 is large and negative, the equilibrium constant for reaction 3, K3, will be large, and this could conceivably produce reasonable quantities of polymers.

Some researchers used the condensing agent dicyanamide (N=CNHC=N) to produce some peptides from glycine, even claiming, ‘dicyanamide mediated polypeptide synthesis may have been a key process by which polypeptides were produced in the primitive hydrosphere.’

However, the biggest problem is that condensing agents would readily react with any water available. Therefore it is a chemical impossibility for the primordial soup to accumulate large quantities of condensing agents, especially if there were millions of years for water to react with them. Yet the Sydney Fox experiment used a 30-fold excess of dicyanamide. And even with these unrealistic conditions, 95% of the glycine remained unreacted, and the highest polymer formed was a tetrapeptide.

 

 

*   Although chemists can make DNA in their laboratories, they can only do so under highly controlled conditions that simulate cytosol. They achieve this by using a pre-existing DNA or gene (template), using the right amount of water, magnesium chloride, and salt buffersand by using a pre-existing microscopic / molecular copy machine called DNA polymerase.  Such would not be the case in nature, since genes are not known to form by themselves, nor even simple proteins that consist of only 8 amino acids: much less complex ones that consist of 900–1000 of them, such as DNA polymerase — along with a motor protein called helicase: that actually spins like a motor (at 1800 rpms) and that unwinds the DNA.

 

**   When two amino acids come together they are called a peptide, and the reaction is called condensation or a condensation reaction **** or dehydration synthesis.  A nucleic acid is a synonym for a nucleotide, and when two or more nucleotides join together they are called an oligonucleotide.

 

***  According to the American Heritage Dictionary of Science, hydrolysis is “a process of decomposition in which a compound is broken down and changed into other compounds by … (absorbing, or being diluted with) water.  For example, in food digestion, the food absorbs water and is broken down by hydrolysis.  The same dictionary says that to hydrolyze means “to decompose by hydrolysis …”  and that organic molecules such as “Nucleic acids, proteins, and polysaccharides contain many bonds that hydrolyze …  In this regard, the combining word hydro- simply means “of or having to do with water.”

 

****  Think of a Condensed can of Campbell’s Soup.  The fact that it is “condensed” simply means that water has been removed.

 

References

1.   http://opus.bibliothek.uni-wuerzburg.de/volltexte/2003/554/pdf/Thesis-complete-2-library.pdf


2.   Peptide Bond at http://en.wikipedia.org/wiki/peptide_bond.


3.   http://biotech.about.com/od/glossary/g/hydrolysis.htm

 

4.   The Creation of Life: a cybernetic approach to evolution, 1970, pp.25-26. Available online through various book sellers. 


5.   
Chemistry by Chance: a formula for non-life, Charles McCombs: Acts & Fact, 2/09, pp. 30-31:www.icr.org/article/4348/  


6    http://en.wikipedia.org/wiki/Cytosol#Water


7.   
Chemistry Refutes Chance Origin of LifePart III, by Jon Covey, B.A.,  and Anita Millen, M.D., M.P.H.,  www.creationinthecrossfire.com/Articles/ChemistryRefutes3.html 


8.   
The Design and Complexity of the Cell,  Jeffrey Tomkins, Ph. D., 2012, pp. 24-25;http://www.icr.org/design-cell/  


9.   Ref. 7 above by Tomkins, p. 79.


10. 
Life, DNA, and Proteins: Why raw materials on earth cannot produce life, at http://in6days.tripod.com/id6.html

 

See more in: EarthAge.com ; CMI

 

 

DNA- fascinating video

Deoxyribonucleic acid (DNA) is a molecule that encodes the genetic instructions used in the development and functioning of all known living organisms and many viruses. Along with RNA and proteins, DNA is one of the three major macromolecules essential for all known forms of life. Most DNA molecules are double-stranded helices, consisting of two long biopolymers of simpler units called nucleotides—each nucleotide is composed of a nucleobase (guanine, adenine, thymine, and cytosine), recorded using the letters G, A, T, and C, as well as a backbone made of alternating sugars (deoxyribose) and phosphate groups (related to phosphoric acid), with the nucleobases (G, A, T, C) attached to the sugars. DNA is well-suited for biological information storage, since the DNA backbone is resistant to cleavage and the double-stranded structure provides the molecule with a built-in duplicate of the encoded information. The following video shows animations of processes which occur within each one of the 10 trillion cells in our body!

Discovery

In 1927, Nikolai Koltsov proposed that inherited traits would be inherited via a “giant hereditary molecule” made up of “two mirror strands that would replicate in a semi-conservative fashion using each strand as a template”. In 1928, Frederick Griffith discovered that traits of the “smooth” form of Pneumococcus could be transferred to the “rough” form of the same bacteria by mixing killed “smooth” bacteria with the live “rough” form. This system provided the first clear suggestion that DNA carries genetic information—the Avery–MacLeod–McCarty experiment—when Oswald Avery, along with coworkers Colin MacLeod and Maclyn McCarty, identified DNA as the transforming principle in 1943. DNA’s role in heredity was confirmed in 1952, when Alfred Hershey and Martha Chase in the Hershey–Chase experiment showed that DNA is the genetic material of the T2 phage.

In 1953, James Watson and Francis Crick suggested what is now accepted as the first correct double-helix model of DNA structure in the journal Nature. Their double-helix, molecular model of DNA was then based on a single X-ray diffraction image (labeled as “Photo 51”) taken by Rosalind Franklin and Raymond Gosling in May 1952, as well as the information that the DNA bases are paired — also obtained through private communications from Erwin Chargaff in the previous years. Chargaff’s rules played a very important role in establishing double-helix configurations for B-DNA as well as A-DNA.

Experimental evidence supporting the Watson and Crick model was published in a series of five articles in the same issue of Nature. Of these, Franklin and Gosling’s paper was the first publication of their own X-ray diffraction data and original analysis method that partially supported the Watson and Crick model; this issue also contained an article on DNA structure by Maurice Wilkins and two of his colleagues, whose analysis and in vivo B-DNA X-ray patterns also supported the presence in vivo of the double-helical DNA configurations as proposed by Crick and Watson for their double-helix molecular model of DNA in the previous two pages of Nature.

Repairing system

It’s interesting to notice that the DNA molecule is highly reactive, thus, very unstable… On a good day about one million bases in the DNA in a human cell are damaged. These lesions are caused by a combination of normal chemical activity within the cell and exposure to radiation and toxins coming from environmental sources including cigarette smoke, grilled foods and industrial wastes. So, the organisms have a handful of repairing mechanisms, as said in a recent Science Daily article:

A number of environmental toxins and chemotherapy drugs are alkylation agents that can attack DNA.

When a DNA base becomes alkylated, it forms a lesion that distorts the shape of the molecule enough to prevent successful replication. If the lesion occurs within a gene, the gene may stop functioning. To make matters worse, there are dozens of different types of alkylated DNA bases, each of which has a different effect on replication.

One method to repair such damage that all organisms have evolved is called base excision repair. In BER, special enzymes known as DNA glycosylases travel down the DNA molecule scanning for these lesions. When they encounter one, they break the base pair bond and flip the deformed base out of the DNA double helix. The enzyme contains a specially shaped pocket that holds the deformed base in place while detaching it without damaging the backbone. This leaves a gap (called an “abasic site”) in the DNA that is repaired by another set of enzymes.

Human cells contain a single glycosylase, named AAG, that repairs alkylated bases. It is specialized to detect and delete “ethenoadenine” bases, which have been deformed by combining with highly reactive, oxidized lipids in the body. However, AAG also handles many other forms of akylation damage. Many bacteria, however, have several types of glycosylases that handle different types of damage.

“It’s hard to figure out how glycosylases recognize different types of alkylation damage from studying AAG since it recognizes so many,” says Eichman. “So we have been studying bacterial glycosylases to get additional insights into the detection and repair process.”

That is how they discovered the bacterial glycosylase AlkD with its unique detection and deletion scheme. All the known glycosylases work in basically the same fashion: They flip out the deformed base and hold it in a special pocket while they excise it. AlkD, by contrast, forces both the deformed base and the base it is paired with to flip to the outside of the double helix. This appears to work because the enzyme only operates on deformed bases that have picked up an excess positive charge, making these bases very unstable. If left alone, the deformed base will detach spontaneously. But AlkD speeds up the process by about 100 times. Eichman speculates that the enzyme might also remain at the location and attract additional repair enzymes to the site.

AlkD has a molecular structure that is considerably different from that of other known DNA-binding proteins or enzymes. However, its structure may be similar to that of another class of enzymes called DNA-dependent kinases. These are very large molecules that possess a small active site that plays a role in regulating the cells’ response to DNA damage. AlkD uses several rod-like helical structures called HEAT repeats to grab hold of DNA. Similar structures have been found in the portion of DNA-dependent kinases with no known function, raising the possibility that they play an additional, unrecognized role in DNA repair.

It’s impossible to conceive that such unstable, complex molecule could have originated all alone, by chance and lasted any long in a pre-biotic environment. In a primordial Earth, with a free-oxygen atmosphere, it turns out that it would have no ozon layer, or a very thin one. Thus, the UV light from the Sun would freely bombards the Earth without filtering; the most damaging UV light types would face no barrier, and it’s a fact that UV light damages, degrades polymers!

Many natural and synthetic polymers are attacked by ultra-violet radiation and products made using these materials may crack or disintegrate (if they’re not UV-stable). The problem is known as UV degradation, and is a common problem in products exposed to sunlight. Continuous exposure is a more serious problem than intermittent exposure, since attack is dependent on the extent and degree of exposure.

Effect of UV exposure on polypropylene rope (the left one is damaged, the right one is a new rope)

Add to it the oxidation problem, hydrolysis, etc… Any natural origin of RNA/DNA is inconceivable!

%d bloggers like this: