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

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

Aromatic properties of 8-hydroxyquinoline and its metal complexes

Abstract Chelatoaromaticity (aromaticity of chelate complexes) has been recently recognized as an important property influencing the stability of chelate compounds. In this paper, aromaticity of various forms of 8-hydroxyquinoline (anion, neutral molecule, zwitterion and cation) as well as its chelate complexes with magnesium and aluminium ions are investigated. Aromatic properties of these compounds are analyzed using several aromaticity indices based on energetic, geometric, magnetic and electronic physical manifestations of this phenomenon. Results of performed calculations have shown different aromatic properties for the two rings (pyridine and benzene) occurring in the studied ligand. Aromaticity of these rings in metal complexes of 8-hydroxyquinoline is significantly higher than that in corresponding ligand anion. This means that during complexation the aromaticity of the ligand increases and the chelatoaromatic effect stabilizes the studied metal complexes. In contrast, metallocyclic rings of studied metal complexes have non-aromatic properties, and, consequently, the metallocyclic ring is not stabilized by chelatoaromaticity. We conclude that, in the complex, every 8-hydroxyquinoline unit and the metal ion are separated p-electronic systems. </jats:p

Evaluation of manure management systems in Europe

The gross value of the agricultural goods in 2014 amounted up to 370 billion Euros. Almost 50% of all agricultural production is provided by livestock farming.Postprint (published version

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

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

Energy and Exergy Assessments of a Diesel-, Biodiesel-, and Ammonia-Fueled Compression Ignition Engine

The research is aimed at investigating ammonia in a compression ignition internal combustion engine as a promising alternative fuel towards decarbonization. This study presents energy and exergy assessments of a low-power engine for three cases of fuel supply, diesel oil, biodiesel oil, and ammonia with pilot biodiesel oil, across the entire engine’s range. While diesel or biodiesel was administered directly into the engine cylinder, the ammonia was delivered through port injection. The results show that the maximum thermal efficiency of 33.56% and exergy efficiency of 31.88% were found at 1800 rpm and 71% load for the diesel fuel system. For the biodiesel fuel system, the efficiencies were 32.72% and 30.93%, respectively, at 1800 rpm and 100% load, and for the ammonia with pilot biodiesel system, they were at 31.98% and 30.04%, respectively, for the same rpm and load. The exergy assessment indicates that exergy destruction, which accounts for the irreversibility of processes such as combustion and friction, is responsible for the greatest loss of useful energy. Optimizing these processes could significantly improve the engine’s performance for all three fuel cases. This research found that ammonia could successfully substitute diesel or biodiesel fuel, as the engine’s efficiency was comparable in all three tested scenarios; however, further research and optimization in terms of the ammonia-fueled engine emissions are required.publishedVersio

Vibrational and quantum-chemical study of pH dependent molecular structures of (hydroxypyridin-4-yl-methyl)phosphonic acid

Abstract Vibrational study of pH dependent molecular structures of (hydroxypyridin-4-yl-methyl)phosphonic acid is discussed based on experimental data and quantum-chemical calculations. A cationic, a zwitteranionic as well as mono-and dianionic forms of the acid are considered in our work. Equilibrium geometries, harmonic vibrational frequencies were calculated for all species of (hydroxypyridin-4-yl-methyl)phosphonic acid deprotonated in different way by using DFT (B3PW91) with 6-31G(d,p) basis set. The computed properties are compared to the experimental values. Additionally, charge distributions and aromaticity index were calculated for species studied here by using generalized atomic polar tensor (GAPT) and harmonic oscillator model of aromaticity (HOMA), respectively