Arsenic in prebiotic species: a theoretical approach

Area of Science:

• Astrochemistry
• Computational Chemistry
• Biochemistry

Background:

• The presence of arsenic in biological systems is a subject of ongoing scientific debate.
• Prebiotic molecules are essential for understanding the origins of life.
• The potential for arsenic to substitute for phosphorus in biological molecules remains an open question.

Purpose of the Study:

• To investigate the stability and potential formation of arsenic-containing prebiotic molecules.
• To computationally assess the feasibility of arsenic replacing phosphorus in biologically relevant structures.
• To provide data that may guide future laboratory experiments.

Main Methods:

• Density Functional Theory (DFT) with B3LYP formalism, MP2, and CCSD(T) methods were employed for computational analysis.
• Systematic computational experiments were performed on simple systems containing [C,H,O,As] and [C,3H,O,As] atoms.
• Comparative analysis of dimethylphosphate (DMP) and dimethylarsenate (DMA) anions was conducted.

Main Results:

• The most stable isomer for [C,H,O,As] was found to be HAsCO.
• For [C,3H,O,As], the peptide-like bond (AsH(2)-CH=O) was not the most stable structure; CH(2)[double bond, length as m-dash]As-OH was more stable.
• The gauche-gauche arrangement is the most stable for both DMP and DMA, suggesting no structural impediment to arsenic inclusion in DNA.
• Analysis revealed a 50% weakening of two As-O bonds in DMA compared to P-O bonds in DMP.

Conclusions:

• Arsenic-containing prebiotic molecules can form stable structures.
• While arsenic can structurally mimic phosphorus in DNA models, it significantly weakens the As-O bonds.
• This weakening suggests that DNA incorporating arsenic instead of phosphorus might be less stable, impacting its structural integrity.