Insights into the molecular interaction between sucrose and α-chymotrypsin.

One of the most important purposes of enzyme engineering is to increase the thermal and kinetic stability of enzymes, which is an important factor for using enzymes in industry. The purpose of the present study is to achieve a higher thermal stability of α-chymotrypsin (α-Chy) by modification of the solvent environment. The influence of sucrose was investigated using thermal denaturation analysis, fluorescence spectroscopy, circular dichroism, molecular docking and molecular dynamics (MD) simulations.

Quantum tunneling recombination in a system of randomly distributed trapped electrons and positive ions.

During the past 10 years, quantum tunneling has been established as one of the dominant mechanisms for recombination in random distributions of electrons and positive ions, and in many dosimetric materials. Specifically quantum tunneling has been shown to be closely associated with two important effects in luminescence materials, namely long term afterglow luminescence and anomalous fading. Two of the common assumptions of quantum tunneling models based on random distributions of electrons and positive ions are: (a) An electron tunnels from a donor to the nearest acceptor, and (b) the concentration of electrons is much lower than that of positive ions at all times during the tunneling process.

An improved procedure for determination of the mean aggregation number of micelles.

In this paper, a theory of fluorescence quenching in micelles which enables a dynamic approach to the evaluation of the aggregation numbers of micelles is presented. This method is based on a detailed kinetic model of quenching of fluorescent probe developed by Tachiya (1975, 1982) and takes into account that a part of quenchers are associated with micelles but the remaining quenchers are in the aqueous phase. The approach presented is an improvement on a previous fluorescence quenching method (Turro and Yekta, 1978) and is applied to determine the aggregation number of sodium dodecyl sulfonate (SAS) in aqueous dipeptide solution using cetylpyridinium chloride as quencher.

Reversible diffusion-influenced reactions of an isolated pair on some two dimensional surfaces.

We investigate reversible diffusion-influenced reactions of an isolated pair in two dimensions. To this end, we employ convolution relations that permit deriving the survival probability of the reversible reaction directly in terms of the survival probability of the irreversible reaction. Furthermore, we make use of the mean reaction time approximation to write the irreversible survival probability in restricted spaces as a single exponential.

Caffeine-mediated detachment of mutagenic ethidium from various nanoscopic micelles: an ultrafast Förster resonance energy transfer study.

In the present study we explore the efficacy of caffeine in dissociating the ethidium (Et) molecule, a model DNA-intercalator as well as a potential mutagen, from nanometer sized micelles of various charges. Steady-state and picosecond-resolved spectroscopic studies on the detachment of Et from various biomimicking micelles of different charges (cationic hexadecyltrimethylammonium bromide (CTAB), neutral (polar) Triton X-100 (TX-100), and anionic sodium dodecyl sulfate (SDS)) reveal the specificity of the caffeine molecule for carrying out such dissociation. The picosecond-resolved Förster resonance energy transfer (FRET) studies between a DNA minor groove binder dye Hoeschst 33258 (H258, donor) and Et (acceptor) have been employed to investigate the alteration in their association in the presence of caffeine at the molecular level.