Structure characterization of [N-phenylamino(2-boronphenyl)-R-methyl]phosphonic acid by vibrational spectroscopy and density functional theory calculations

We present the first Fourier-transform infrared absorption (FT-IR) and Fourier-transform Raman (FT-Raman) analysis of vibrational structure of [N-phenylamino(2-boronphenyl)-R-methyl]phosphonic acid ([PhN-(2-PhB(OH)2)-R-Me]PO3H2). Assignments of experimental wavenumbers are based on performed theoretical calculations using density functional theory (DFT). Theoretical calculations show that the most stable structure of the investigated molecule is dimer in cis-trans conformation created by a pair of intermolecular hydrogen bonds between the boron hydroxyl groups of two monomers

Subunit-Selective Interrogation of CO Recombination in Carbonmonoxy Hemoglobin by Isotope-Edited Time-Resolved Resonance Raman Spectroscopy

Hemoglobin (Hb) is an allosteric tetrameric protein made up of αβ heterodimers. The α and β chains are similar, but are chemically and structurally distinct. To investigate dynamical differences between the chains, we have prepared tetramers in which the chains are isotopically distinguishable, via reconstitution with 15N-heme. Ligand recombination and heme structural evolution, following HbCO dissociation, was monitored with chain selectivity by resonance Raman (RR) spectroscopy. For α but not for β chains, the frequency of the ν4 porphyrin breathing mode increased on the microsecond time scale. This increase is a manifestation of proximal tension in the Hb T-state, and its time course is parallel to the formation of T contacts, as determined previously by UVRR spectroscopy. Despite the localization of proximal constraint in the α chains, geminate recombination was found to be equally probable in the two chains, with yields of 39 ± 2%. We discuss the possibility that this equivalence is coincidental, in the sense that it arises from the evolutionary pressure for cooperativity, or that it reflects mechanical coupling across the αβ interface, evidence for which has emerged from UVRR studies of site mutants

Colloidal Metal Surfaces as Biosensors of Biological Samples

Colloidal solutions of silver (AgNPs), gold (AuNPs), and platinum nanoparticles (PtNps) obtained under controlled conditions in an aqueous media by chemical methods were used as effective biosensors of biological compounds such as bombesins (BN). The BN adsorption at the metal/aqueous interface was investigated by surface-enhanced Raman scattering (SERS). Briefly, the spectral pattern of BN in the silver, gold, and platinum sols is strongly influenced by the indole ring vibrations of L-tryptophan at position 8 of the amino acid sequence (Trp8). In addition, L-methionine (Met) at the C-terminus determines the BN adsorption, mainly onto the AuNPs and AgNPs surfaces

Pyrolytic carbons derived from water soluble polymers

Conductive pyrolytic carbon materials were obtained in wet impregnation process followed by controlled pyrolysis. Poly- N -vinylformamide (PNVF) as well as mix- ture of PNVF and pyromellitic acid (PMA) were applied as carbon precursors. Composition of carbon precursors was optimized in terms to obtain best electrical properties of pyrolytic carbons. Mixture of PNVF and PMA as well as pure PNVF were deposited on the model alumina ( a -Al 2 O 3 ) support to form conductive carbon layers (CCL). The opti- mal composition of the polymer precursors was determined by Raman spectra and electrical conductivity measurements. The carbonization conditions were optimized using com- plementary thermal analysis methods (EGA(FTIR)–TG/ DTG/STDA). It was found that the addition of PMA to polymer precursor PNVF decreases temperature of forma- tion of condensed graphene structures, domains of electrical conductivity, thus, the formation temperature of pyrolytic carbons with desired electrical properties may be decreased