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C Ponnamperuma

Publications and source records attributed to C Ponnamperuma.

At least 19 recordsLinked to original sources
PubMed1990

Nonrandomness in prebiotic peptide synthesis.

We have synthesized and studied the properties of phosphoanhydrides of alanine with guanosine monophosphate, uridine monophosphate, and adenosine monophosphate. This series of compounds allowed us to investigate the specificity of peptide bound formation in a reaction that could have taken place on the prebiotic earth. We asked whether the intrinsic reactivity of the amino acids, the nature of the nucleotide in the anhydride, or the complementary polynucleotide template influences the specificity of the peptide synthesis reaction. We observed that the differential reactivity of the amino acids results in nearest-neighbor preferences during the peptide synthesis, whereas the nature of the nucleotides and the presence of complementary polynucleotides had no influence on the specificity. These results suggest that some peptides would have been more abundant than others on the prebiotic earth and have implications for the study of the origins of the genetic code and protein synthesis.

Amino Acid Sequence↗
PubMed1985

Trace elements in chemical evolution, I.

Research on trace elements in chemical evolution is reviewed from three points of view. They are: the origin of the essentiality of trace elements in present biological systems; the possible roles of trace elements in chemical evolution; and the origin of enzymatic activity with metal ions, i.e., the origin of metalloenzymes.

Amino Acids↗
PubMed1985

Trace elements in chemical evolution. II: Synthesis of amino acids under simulated primitive earth conditions in the presence of trace elements.

Electric discharge experiments have been performed in a plausible primitive earth atmosphere consisting of methane, nitrogen, and water over an aqueous phase of an ammonia-ammonium buffer solution. In some experiments, ions of metal elements, calcium, magnesium, zinc, iron and molybdenum were introduced. Gas phase products and amino acids in the liquid phase were analyzed by gas chromatography. With trace metal ions, less organic compounds in the gas phase and larger amounts of amino acids were obtained than without them. The results have shown the possible importance of trace elements in chemical evolution and the origin of life on the earth.

Amino Acids↗
PubMed1985

Synthesis and properties of an all-D model ribonuclease S-peptide.

In order to examine the effect of a defined enantiomeric sequence on protein structure, the all-D model ribonuclease S-peptide, H-Ala-Glu-Ala4-Lys-Phe-Ala-Arg-Ala-His-Met-Ala2-OH, has been synthesized by the solid phase method. The all-L peptide has been synthesized previously and shown to possess 36% of ribonuclease S activity when added to ribonuclease S-protein (Komoriya, A. & Chaiken, I.M. (1982) J. Biol. Chem 257, 2599-2604). The synthetic D-peptide was purified by gel filtration and semipreparative reverse phase HPLC. Amino acid composition of the synthetic peptide was in agreement with theory and gas chromatographic analysis showed that no significant racemization had occurred during synthesis. Circular dichroism (CD) studies of the D-peptide showed a peak of positive ellipticity in the 220-230 nm region, whereas a negative ellipticity peak for the L-peptide was observed. The effects of temperature and trifluoroethanol on the far-ultraviolet CD spectra of D- and L-peptides were similar but of opposite sign, confirming the expectation that the D-peptide has the propensity to form an alpha-helical structure which is enantiomeric with respect to that formed by the L-peptide. In the presence of S-protein, the L-peptide showed hydrolytic activity against the substrate cytidine-2':3'-monophosphate, whereas the D-peptide was inactive. Addition of the D-peptide to mixtures of L-peptide and S-protein did not lead to inhibition of enzymatic activity. These results indicate lack of binding of D-peptide to S-protein to produce either an active or inactive species.

Amino Acid Sequence↗
PubMed1979

Amino acids in a carbonaceous chondrite from Antarctica.

A carbonaceous chondrite from the Antarctic, referred to as the Allan Hills meteorite 77306, appears to be free from terrestrial organic contamination. The presence of both protein and non-protein amino acids and an equal abundance of D- and L-enantiomers of amino acids, is testimony to the extraterrestrial nature of these compounds.

Amino Acids↗
PubMed1977

Evidence for amino acids in hydrolysates of compounds formed by ionizing radiations. I. Aqueous solutions of HCN, NH4CN, and NaCN.

Dilute, 02-free aqueous cyanides were exposed to multikilorad doses of a radioactive cobalt source. After the removal of unreacted cyanides and of volatile radiolytic products, the residue was hydrolyzed and the resulting material analyzed for amino acids. The results show the presence of five protein amino acids and five amino acids which do not occur in natural proteins. The amino acids of enantiomeric derivatives separated on an optically active column, appeared to consist of approximately equal amounts of D and L isomers. Radiation-chemical yields of amino acids were determined at various radiation doses. The results obtained support the previous findings that the free-radical initiated process is the source of oligomers which on hydrolysis release the amino acids.

Amino Acids↗
PubMed1977

Evidence of amino acids in hydrolysates of compounds formed by ionizing radiations. II. Aqueous solutions of CH3CN and C2H5CN.

It has been shown that the action of ionizing radiations on dilute, oxygen-free, aqueous solutions of acetonitrile and propionitrile leads to the formation of oligomers, which upon hydrolyses release amino acids. The presence of nine amino acids, the same as those found in irradiated aqueous cyanides, has been established. those amino acids with asymmetric carbon atoms separated by GC method, appeared to consist of nearly equal amounts of D and L isomers. Glycine is the most abundant amino acid in hydrolysates of acetonitrile, while alanine appears in the samples of propionitrile. A comparison of all amino acids, identified in hydrolysates of various cyanides and nitriles, suggests that it is the cyano group, and a free-radical initiated mechanism, that is primarily involved in these radiation-chemical changes of potential interest to prebiotic chemistry.

Acetonitriles↗
PubMed1977

Phosphorus, a key to life on the primitive Earth.

The phosphorus of the primitive Earth was present as phosphates. It is strongly probably that a portion of the phosphate was present as condensed phosphates. The primitive Earth was highly deficient in the total available phosphorus until a sufficient quantity of phosphorus weathered from the igneous rocks in which it was entrapped. Approximately three billion years were required for the seas to become saturated. Until this time passed the seas acted as a giant sink for phosphorus, diluting it to the extent that all forms of life were deprived of the vital nutrient. When the seas became saturated, the rate of turn over of the phosphorus increased rapidly. As the seas pulsated, they left the excess precipitate phosphorus as sedimentary rock in locally righ deposits on which life could thrive.

Apatites↗
PubMed1976

Formation of biologically relevant carboxylic acids during the gamma irradiation of acetic acid.

Irradiation of aqueous solutions of acetic acid with gamma rays produced several carboxylic acids in small yield. Their identification was based on the technique of gas chromatography combined with mass spectrometry. Some of these acids are Krebs Cycle intermediates. Their simultaneous formation in experiments simulating the primitive conditions on the earth suggests that metabolic pathways may have their origin in prebiotic chemical processes.

Acetates↗
PubMed1976

Prebiotic condensation reactions in an aqueous medium: a review of condensing agents.

Biopolymers are formed by dehydration-type condensation reactions. In aqueous solutions dehydration reactions are very unlikely to happen spontaneously. However, coupling of dehydration-condensation to the hydrolysis of condensing agents could facilitate the synthesis of biopolymers in an aqueous solution. The literature shows that the peptides, nucleosides, nucleotides and oligonucleotides can be formed in this way. A careful study of the literature pertaining to prebiotic condensing agents was conducted in order to determine the most plausible prebiotic synthesis of biopolymers. The condensing agents taken into consideration are cyanamide, carbodimide, dicyanamide, dicyandiamide, hydrogen-cyanide-tetramer, cyanogen and the linear- and cyclic polyphosphates. From both a chemical as well as biological point of view the polyphosphates appear to be the most plausible general prebiotic condensing agent.

Biopolymers↗
PubMed1975

Search for amino acids in Apollo returned lunar soil.

The lunar samples from Apollo flights 11 through 17 provided the students of chemical evolution with an opportunity of examining extraterrestrial materials for evidence of early prebiological chemistry in the solar system. Our search was directed to water-extractable compounds with emphasis on amino acids. Gas chromatography, ion-exchange chromatography and gas chromatography combined with mass spectrometry were used for the analysis. It is our conclusion that amino acids are not present in the lunar regolith above the background levels of our investigations.

Amino Acids↗