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In the present study, the isomeric forms of a biologically active 2-aminopyrimidinium picrate (2APP) cocrystal were investigated using spectroscopic measurements (FT-IR and FT-Raman) and density functional theory calculations. The vibrational assignments of IR and Raman peaks were predicted and the experimental FT-IR and FT-Raman spectra of the condensed phase of 2APP were compared with the simulated one. The intrinsic reaction coordinate (IRC) analysis was performed on all the possible reaction pathways to identify the isomeric forms of 2APP and transition state geometry. From the IRC analysis, a relatively stable form (named as isomer 2) has been identified in addition to the existing isomeric form (isomer 1) in the crystalline packing of 2APP. The presence of non-covalent interactions within the isomeric forms of 2APP was investigated with the help of quantum topological atoms in molecules analysis. Reactivity descriptors and charge delocalization from lone pair to acceptor entities of both the isomers were predicted to validate the interactions present in the molecule and also to understand the charge distribution within the molecule. [ABSTRACT FROM AUTHOR]

Ethanimine (CH3CHNH) is an important prebiotic molecule since it is a precursor of amino acid α-alanine in Strecker synthesis. Two isomers (E and Z) of ethanimine were detected in the molecular cloud Sagittarius B2 north during GBT-PRIMOS survey. A possible radical-molecule reaction pathway has been proposed for the formation of ethanimine in the interstellar medium (ISM) from some previously detected interstellar molecules like methylene (both triplet CH2 (3B1) and singlet CH2 (1A1)) and methyenimine (CH2NH). The mechanism has been studied in the gas phase and in water ice with the help of density functional theory at B2PLYPD/6-311++G (2d, p) level of theory. It is observed that E-ethanimine forms efficiently in gas phase but ice reactions are favorable only in the hot core of molecular clouds. Same is true for the formation of Z-ethanimine which forms only at the surface of water cluster as the height of entrance barrier for formation of Z-ethanimine is similar to that of E-ethanimine. Isomerization from E to Z form is also studied and found to be forbidden due to large entrance barrier. Out of the two reaction system CH2 (3B1) + CH2NH and CH2 (1A1) + CH2NH, later is more favorable then the former one due to the small entrance barrier. Still, much of the detected abundance of ethanimine comes from the reaction of CH2 (3B1) with CH2NH as since CH2 (1A1) has very low abundance compared to the CH2 (3B1) in ISM. The proposed pathway seems to be a promising candidate for the ethanimine formation in ISM. [ABSTRACT FROM AUTHOR]

Metal nanoclusters have several applications in biological processes, medicine, cancer therapy, catalysis, etc. Iridium (Ir) nanoclusters exhibit excellent detection behavior compared to their bulk material. This work includes a deep insight into the interaction of Ir nanoclusters of four atoms (Ir 4 ) with amino acids and the analysis of Ir-amino acid (Ir-AAc) complexes. UV-visible spectroscopy of the Ir 4 nanocluster, amino acids, and their complexes was discussed as a way to detect amino acids with the help of the Ir 4 nanocluster. In UV-visible analysis, the UV-visible peak of phenylalanine (Phe) appeared at 204 nm with an excitation energy of 6.02 eV with a 0.0516 oscillator strength. Meanwhile, only in the Ir 4 nanocluster-phenylalanine (Ir-Phe) complex, the UV-visible peak was observed at 661 nm with an excitation energy of 1.87 eV and oscillator strength of 0.0051. This peak was observed due to the transition from HOMO-1 to LUMO+3. In the other complexes, no UV-visible peaks are observed. Thus, the results predict that the Ir 4 nanocluster can be used in the detection of Phe via UV-visible spectra., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Research on amino acids is an attractive area because of their application in metabolism, cancer treatment, growth, and repair of body tissue, and RNA and DNA syntheses. Twenty amino acids are primarily responsible for protein synthesis. In our study, we used a Cu 6 nanocluster as an amino acid detector. For the investigation, we adsorbed amino acids on the Cu 6 nanocluster and studied their UV-visible spectra. It is observed that all of the Cu 6 -amino acid complexes have peaks at near 380 nm wavelength except the Cu-phenylalanine complex, where two UV-visible peaks are found at wavelengths 351 nm (excitation energy 3.49 eV) and 403 nm (excitation energy 3.02 eV), respectively, which originated from the HOMO - 2 to LUMO (28%) and HOMO - 1 to LUMO (38%) transitions. Due to this unique transition, the Cu 6 nanocluster can be used for the detection of the phenylalanine amino acid out of the 20 amino acids., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)