Search results for "Biomolecule"
showing 10 items of 666 documents
Protonation-induced fluorescence modulation of carbazole-based emitters
2022
The development of purely organic fluorescence emitters is of great importance for their low cost and high performance. Responding to this demand, carbazole is a promising emitter due to its extensive freedom for functionalisation, high thermal and chemical stability, as well as low cost. Herein, the effect of protonation on the fluorescence of various pyridine-functionalised carbazole-based bipolar host materials was studied both in solution and in the solid-state. The restriction of intramolecular rotation of the molecules upon protonation of the pyridyl-moiety together with easier planarization of the protonated acceptor and the donor moieties and relocalisation of the LUMO orbital on th…
Amino acid chemistry in solution: structural properties and vibrational dynamics of serine using density functional theory and a continuum solvent mo…
2004
A structural and vibrational study of amino acid serine in aqueous solution has been carried out using Fourier transform spectroscopies and quantum mechanical calculations. FT-IR and FT-Raman spectra of serine in H2O and D2O solutions were recorded and a general assignment of the observed bands was proposed on the basis of a zwitterionic structure for serine. Main criteria were the observed wavenumber shifts upon deuteration and previous assignments for other amino acids. A quadratic force field was computed using ab initio methodology at the 6-31+G** level and the hybrid functional B3LYP. The solvent effect was simulated by placing the serine molecule into an ellipsoidal cavity surrounded …
Transition structures for hydride transfer reactions in vacuo and their role in enzyme catalysis
1996
A general discussion as to the role of in vacuo transition structure in enzyme catalysis is presented. Quantum mechanical aspects are emphasized. The transition structures defined as saddle points ...
Snapshots of a solid-state transformation: coexistence of three phases trapped in one crystal† †Electronic supplementary information (ESI) available:…
2016
Solvent extrusion leads to crystallographic–magnetic transition within a molecular complex via an intermediate that can be trapped and characterized.
HIGHLY EXCITED VIBRATIONAL STATES OF CYCLIC MOLECULES INVESTIGATED BY I.C.L.A SPECTROSCOPY WITH PHOTOACOUSTIC DETECTION
1991
The spectra of the fourth and fifth CH stretching overtones of cyclohexene and cyclopentene molecules and of some of their selectively deuterated derivatives have been measured by dye laser intracavity spectroscopy with photoacoustic detection. The intramolecular relaxation of the vibrational energy occurs principally through Fermi resonances with CH2 bending combinations in cyclohexene and through a coupling between the stretching and the ring puckering motions in cyclopentene.
Elastic properties of DNA linked flexible magnetic filaments.
2011
Elastic properties of magnetic filaments linked by DNA in solutions of univalent and bivalent salts with different pH values are investigated through their deformation in an external field. A strong dependence of the bending modulus in bivalent salt solution on the pH is shown. Experimental results are interpreted on the basis of the magnetic elastica.
Influence of Dynamics on The Analysis of Solid-State NMR Data From Membrane-bound Peptides
2009
By isotope labeling of membrane-bound peptides, typically with 2H, 19F, or 15N, solid-state NMR experiments can yield data from which the orientation of peptides in a native membrane environment can be determined. Such an orientation is defined by a tilt angle and an azimuthal rotation angle.Here we show that to obtain correct values of the orientation angles, it is important to include dynamics in the analysis of the NMR data. Nevertheless the effects of dynamics are different depending on the type of isotope labeling and NMR experiment considered.To analyze the influence of dynamics in detail, we generated virtual NMR observables using a model peptide undergoing explicit Gaussian fluctuat…
Homopolymer adsorption on periodically structured surfaces in systems with incommensurable lengths
2013
Surface-induced selective adsorption of homopolymers on a generic level is numerically analyzed for freely jointed chains (with a fixed bond length) whose monomers are attracted by the sites of regular periodic patterns. In particular, the behavior of the specific heat, the gyration tensor, and the bond order tensor are investigated as functions of the temperature. The properties of the transition are related to the interplay of the characteristic lengths. The adsorption proceeds in two steps for certain incommensurabilities of the bond length and the lattice constant. The corresponding adsorption mechanisms are elucidated by looking at the evolution of the inter bond angle distribution upo…
Difficulties of density functional theory in predicting the torsional potential of 2,2?-bithiophene
1998
The internal rotation of 2,2′-bithiophene was investigated within the density functional theory (DFT) approach. Fully optimized DFT torsional potentials are compared with Moller–Plesset (MP2) results which predict a fourfold potential with s-cis- and s-trans-gauche minima. DFT calculations fail in describing the energetics of the internal rotation because they favor planar vs. perpendicular conformers. Gradient-corrected functionals provide torsional potentials where the gauche minima have almost vanished and the s-ciss-trans interconversion barriers are twice as high as the barriers obtained at the MP2 level. The use of local functionals augments the shortcomings of the DFT approach. The g…
Mechanical unfolding pathway of a model β-peptide foldamer.
2015
Foldamers constructed from oligomers of β-peptides form stable secondary helix structures already for small chain lengths, which makes them ideal candidates for the investigation of the (un)folding of polypeptides. Here, the results of molecular simulations of the mechanical unfolding of a β-heptapeptide in methanol solvent revealing the detailed unfolding pathway are reported. The unfolding process is shown to proceed via a stable intermediate even for such a small system. This result is arrived at performing non-equilibrium force ramp simulations employing different pulling velocities and also using standard calculations of the potential of mean force, i.e., the free energy as a function …