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.
Portland State University, Portland, Oregon 97201, USA. rpopa@pdx.edu
Radu
R
Popa
Vily Marius
VM
Cimpoiaşu
Romulus Ion
RI
Scorei
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