Rooting prebiotic chirality in spinomeric chemistry?
Spinomeric chemistry is a domain of physical chemistry that explores the role of spin-isomery in chemical reactivity. In large magnetic fields (B), chemical structures with three adjacent nuclear spins (such as H(2)(17)O, H(2)(33)S,-NH(2), and and -(13)CH(2)-) form complex spinomers. Known departure from a 1:1 ratio between various types of spinomers opens interesting research avenues in their potential role in asymmetric hydration processes. Recent time domain (1)H nuclear magnetic resonance (TD-(1)HNMR) findings revealed the existence of small, yet consistent, H(2)(17)O-controlled enantio-different proton exchange reactivity in sugars. The mechanisms behind this effect are unclear and may involve spinomer/enantiocenter (e.g., H(2)(17)O/*C) interactions or spinomer/spinomer (e.g., H(2)(17)O/-NH(2)) interactions. We developed an experimental model that allows for the verification and study of such effects. We used TD-(1)HNMR at 0.589 T to study and compare proton exchange enantio-differences in asparagine (Asn) and mandelic acid in response to titration with H(2)(17)O at constant pH. Unlike Asn, mandelic acid has no complex spinomer group (such as -NH(2)) in its chiral center. We report finding enantio-differences regarding DeltapK and 1/T(2)(0) correlated with H(2)(17)O, and linear changes in DeltaM(2) indicating differences in the affinity of enantiomers for H(2)(17)O surface hydration. These results stress the importance of H(2)(17)O-based spinomeric chemistry in chiral reactivity and open windows toward a novel interpretation of the origin of prebiotic chiral reactivity in the presence of moderately large B (such as on magnetic mineral surfaces or on satellites of gaseous giants), as well as toward abiotic isotopic fractionation of H(2)(17)O in the presence of chiral organic molecules.
Popa
Radu
R
Portland State University, Portland, Oregon 97201, USA. rpopa@pdx.edu
Cimpoiaşu
Vily Marius
VM
Scorei
Romulus Ion
RI
D001216:Asparagine / Q000737:chemistry; D002627:Chemistry, Physical; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007536:Isomerism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008333:Mandelic Acids / Q000737:chemistry; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry; D011522:Protons; D013997:Time Factors; D014867:Water / Q000737:chemistry
D008333:Mandelic Acids; D011522:Protons; D014867:Water; D001216:Asparagine; C037938:mandelic acid; D010100:Oxygen