D-Serine

Amino acids play important roles in human pathology and physiology and the qualitative and quantitative determination of chiral amino acids in humans and mammals also has important impacts on the life sciences. Therefore, the introduction of artificial probes to assess the concentrations and enantiomeric compositions [ee = ([D] - [L])/([D] + [L])] of amino acids in aqueous solution is necessary in understanding certain biological processes and diagnosing and treating diseases. Herein, a bifunctional achiral coumarin probe (Br-Coumarin) is reported to determine the absolute configuration, ee value, and concentration of 16 amino acids in THF/H₂O = 1/4 solution at micromolar concentrations. The effectiveness and practicability of the sensing methods are illustrated through the evaluation of various ee values and concentrations of Cys, Pro, and Phe samples with good accuracy. Besides, the reactions of the probe with various amino acids exhibit different colors under daylight or UV light (365 nm). Particularly, Br-Coumarin can be used to visually detect Cys, Lys, Arg, and Pro with high selectivity under both daylight and UV light (365 nm) and exhibits excellent selectivity and sensitivity for the fluorescent recognition of Cys.

Factors governing electron transfer (ET) in proteins and peptides are widely studied due to the role of ET in biol. important processes.One of them is the influence of the optical configuration of amino acids on the ability of peptides to aggregate into ensembles: dimers, oligomers, fibrils.Such assemblies, called amyloids, are known to contain D-isomers of asparagine and serine, and their presence in aging living organisms leads to a number of diseases, including Alzheimer's disease.However, how these amino acids affect the structure and properties of peptides have not yet been established.Using the example of the pentapeptide (PP)-(L)histidine-(L)asparagine-(L)serine-glycine-(L)tyrosine and its analogs with D-asparagine and D-serine, this article studies the comparative reactivity of optical isomers in photoinduced ET using chem. induced dynamic nuclear polarization (CIDNP), fluorescence spectroscopy and quantum chem. calculationsThe CIDNP method was chosen because it had previously demonstrated high sensitivity to ET processes in chiral dyads linked by non-covalent interactions.ET involving Tyr and His residues of PP was detected under UV irradiation both in the presence of an electron acceptor, naproxen, and during photolysis of PP itself.It was shown that the efficiency of ET and PP fluorescence quenching differ for optical isomers of asparagine and serine.In addition, the dependence of the CIDNP efficiency on the PP concentration showed that ET between Tyr and peptide bonds can occur in the dimer of the PP.Quantum chem. calculation confirm the possibility of PP self-association