Synthesis,structure, and photoluminescence properties of bis[2-(1,3-benzoxazol-2-yl-κ<Emphasis Type="Italic">N</Emphasis>)-4,5-dichloro-3-(ethoxycarbonyl)phenolato-κ<Emphasis Type="Italic">O</Emphasis>]zinc(II)

The structure of bis[2-(1,3-benzoxazol-2-yl-κN)-4,5-dichloro-3-(ethoxycarbonyl)phenolato-κO]-zinc(II) was determined by IR and ¹H and ¹³C NMR spectroscopy, and its structural characteristics were estimated by quantum chemical calculations. The complex showed photoluminescence properties.     

Properties and <Emphasis Type="Italic">N</Emphasis>-glycosylation of recombinant endoglucanase II from <Emphasis Type="Italic">Penicillium verruculosum</Emphasis>

Cellulases are the main components of enzyme complexes used in biotransformation processes of plant raw materials into valuable commercial products. Endoglucanase II (EG II) from the Penicillium verruculosum fungus was cloned into Penicillium canescens. The homogeneous recombinant EGII form is isolated and its properties are studied in comparison with the native enzyme. The N-glycosylation sites and the structure of the N-linked glycans are been determined using mass spectrometry. The biochemical and catalytic properties, as well as the N-glycosylation type of the obtained recombinant EGII form, appear to be close to the native enzyme. At the two potential N-glycosylation sites (N42 and N194) of both forms of the enzyme, N-linked high mannose glycans (or their enzymatic “trimming” products) according to the general formula (Man)_1–9(GlcNAc)₂ are detected. No glycosylation is found at the third potential site (N19).     

Synthesis and structural studies of 5,7(4,6)-di(<Emphasis Type="Italic">tert</Emphasis>-butyl)-2-(6,8-dimethyl-4-chloroquinolin-2-yl)-1,3-tropolones by quantum-chemical methods and two-dimensional correlation NMR spectroscopy

4,6-Di(tert-butyl)-2-(quinolin-2-yl)-1,3-tropolone (7′) was isolated for the first time from the acid-catalyzed reaction of 2-methyl-substituted nitrogen heterocycles with 1,2-benzoquinones, which proceeds with the expansion of the o-quinone ring to give mainly isomeric 5,7-di(tert-butyl)-2-(quinolin-2-yl)-1,3-tropolone.     

Detection of major xylanase-containing cellulose-binding domain from Penicillium verruculosum by combination of chromatofocusing and limited proteolysis

Adsorption on microcrystalline cell ulose of enzyme components of cellulase complex from Penicillium verruculosum was studied by chromatofocusing on a Mono P column. The most strongly adsorbed and major component was identified as xylanase (XYN) with MW 65 k Da and pl 4.5. The high adsorption degree of XYN on cellulose indicated the possible presence of a cellulose-binding domain in the molecular sturcture. Limited proteolysis of XYN with papain was carried out. Kinetics of proteolysis was monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis and measuring activities toward insoluble xylan and 4-methylumbelliferyl-β-d-lactoside (MUF-LAC). During the proteolysis, formation of two polypeptides with MW 51 and 14k Da was observed. No loss of activity toward thesolu blesubstrate was observed, wherease the activity toward xylan decreased rapidly. Adsorption distribution coefficient (K _d) of the core protein separated by gel-filtration was found to be 15 times lower than the K _d for the initial nondigested XYN (0.02 and 0.29 L/g, respectively). The activity of core protein toward insoluble xylan was close to zero, whereas the activity toward MUF-LAC was close to that exhibited by the original enzyme. The results presented indicate a bifunctional organization of XYN, where one domain acts as a binding anchor for insoluble substrates and the other, localized in the core protein, contains the active site.     

Thermodynamics of Formation of Molecular Complexes of Aromatic Nitro Derivatives with Lincomycin and β-Glycyrrhizic Acid

It was found that lincomycin and -glycyrrhizic acid form 1:2 molecular complexes with aromatic nitro derivatives. Quantum-chemical calculations of lincomycin and -glycyrrhizic acid were performed. These compounds form a cavity and, like podands, are capable of accommodating guest molecules. The formation constants and the thermodynamic characteristics of the complexes were calculated. A linear correlation was found between the formation constants of the molecular complexes of -glycyrrhizic acid and the Hammett constants of the substituents in the nitro derivatives. The complexes of lincomycin and -glycyrrhizic acid with aromatic nitro derivatives are formed by a common mechanism involving related bonds.     

Effect of structural and physico-chemical features of cellulosic substrates on the efficiency of enzymatic hydrolysis

Effects of major physicochemical and structural parameters of cellulose on the rate and degree of its enzymatic hydrolysis were tested with cellulosic materials from various sources. Some different pretreatments were: mechanical (milling), physical (X-ray irradiation), and chemical (cadoxen, H₃PO₄, H₂SO₄, NaOH, Fe²+/H₂O₂). The average size of cellulose particles and its degree of polymerization had little effect on the efficiency of enzymatic hydrolysis. For samples of pure cellulose (cotton linter, microcrystalline cellulose, α-cellulose), increase in the specific surface area accessible to protein molecules and decrease in the crystallinity index accelerated the enzymatic hydrolysis (the correlation coefficients were 0.89 and 0.92, respectively). In the case of lignocellulose (bagasse), a quantitative linear relationship only between specific surface area and reactivity was observed.     

An Exceptional Set in the Ergodic Theory of Markov Maps of the Interval

It is known that a Markov map T of the unit interval preservesa measure µ, say, equivalent to Lebesgue measure, andthat almost every point of the interval has a forward orbitunder T that is uniformly distributed with respect to µ.In the opposite direction the main result of this paper statesthat there is a set of points having Hausdorff dimension 1 whoseforward orbits are in a certain sense very far from being sodistributed. 1991 Mathematics Subject Classification: 58F08,28A80.     

A new spectrophotometric method for determination of furfural and pentoses

A spectrophotometric method for determination of furfural and pentoses based on their color reaction with sulfuric acid in the presence of mercury(II) was developed.