Possible Origin for Porphin Derivatives in Prebiotic Chemistry – A Computational Study

Abstract

A set of chemical reactions is postulated to account for the formation of the macrocyclic porphin structure, basic to the pyrrole derivatives chlorophyll, protoporphyrin, heme and bilirubin, important in photosynthesis, respiration and digestion. A set of equations is given for the prebiotic synthesis of porphin derivatives from the simple molecules; cyanoacetylene, diacetylene, carbon monoxide and ammonia that have been detected in space. A number of isomers of hydrogenated porphin arise which may lose hydrogen to give ultimately porphin and its dehydrogenated derivative. The reactions, while not unique, provide a pathway which has been shown to be feasible from the overall enthalpy changes in the ZKE approximation at the HF and MP2/6-31G* level.

A Prebiotic Surface Catalysed Photochemically Activated Synthesis of L-Cysteine

“…The standard calculations at the HF and MP2 levels including zero-point energy corrections [13], together with scaling [14], using the same basis set, 6-31G*, are as previously published [5]. Enthalpy changes at the HF level not including scaled zero point energies are designated as ΔH.…”

“…From a prebiotic perspective [5] it is desirable if the reactant molecules formed spontaneously from a supposed prebiotic atmosphere to be inevitably present. It has often been held that the atmosphere of the Earth was originally mildly reducing [2,6] implying the presence of concentrations of carbon monoxide, ammonia, water, hydrogen and hydrogen sulfide.…”

Simple Formation of an Abiotic Porphyrinogen in Aqueous Solution

“…In this regard, a prebiotically plausible route to tetrapyrrole molecules has yet to be demonstrated (Miller 1986(Miller , 1987(Miller , 1998, at least in the context of robust reaction of simple species in anaerobic aqueous solution to give measurable quantities of stable product. This dearth exists despite extensive studies in the half-century since Miller's seminal spark-discharge experiments (for a review of early work, see : Wnuk 1983; for more recent work, see : Scott 1997;Aylward and Bofinger 2005;Ksander et al 1987;Meierhenrich et al 2005).…”

Metal‐Free Activation of CO2 by Mesoporous Graphitic Carbon Nitride

“…[1,2] Interestingly, in current photosynthetic systems, this process relies on the formation of a carbamate as the first step of the cycle, [3] which may also have been the case in prebiotic systems, as a number of cyanide-based, nitrogen-rich, conjugated organic molecules, such as nucleic acids, porphyrins, and phthalocyanines, existed before life began. [4] In synthetic chemistry, numerous transition-metal catalysts for the activation of CO 2 have been explored. [5,6] Previous metal-free attempts concentrated on the use of alkylated amidines and guanidines, [7][8][9][10] such as 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU, 1, Scheme 1).…”