Discontinuous native protein gel electrophoresis

Analysis of the oligomeric state of a native protein usually requires analytical ultracentrifugation or repeated gel filtration to calculate the protein's size. We have developed a discontinuous native protein gel electrophoresis system that allows the separation of even basic proteins according to their size, oligomeric state, and shape. This gel system combines the addition of negative charges to the proteins by Serva Blue G with a discontinuous buffer system and gradient gels. As in SDS-PAGE, chloride constitutes the high mobility anion in the gel and anode buffer. However, for sample focusing this system employs histidine instead of glycine as the slow dipolar ion following from the cathode buffer to improve migration of basic proteins. In addition, proteins run into gel pores corresponding to their size and shape in the gradient gel. Using this gel system, we show that the polypyrimidine tract-binding protein (PTB) is a monomer.     

Microfibrillar carbon from native cellulose

Use of pyrolytic carbon from cellulose has been limited in practice to activated adsorbent carbon, but cellulose-derived carbon retaining the nanoscale microfibrillar morphology offers rich possibilities as an advanced material. Here we developed novel methods to prepare such materials by an improved drying of wet cellulose prior to pyrolysis. This procedure is an adaptation from electron microscopy techniques, i.e. rapid freeze drying of suspension and solvent exchange drying, both being effective in preventing coagulation of cellulose microfibrils/microcrystals. Pyrolytic carbon from such material has a large external surface area, with the graphitic carbon crystallites roughly aligned along the fiber axis. These features are potentially useful in developing novel carbon nanomaterials for electrodes, catalyst supports, or composite material elements.     

A native cellulose microfibril model

To aid in the understanding of cellulose ultrastructure, computer modelling has been employed to create a model of monoclinic (I) native cellulose. This was achieved by building a chain of cellulose, which was used in a two chain unit cell. An energy minimized microfibril model was created from several of these unit cells. A major advantage of this model is that it is a large scale unconstrained, isolated system. Thus, it facilitates the study of surface as well as central chains and provides a working model of a cellulose microfibril. An extensive analysis was carried out of intermolecular non-bond interactions and how they might contribute to the stability of the structure of crystalline native cellulose. 0969--0239 © 1998 Blackie Academic & Professional     

Biosensors based on native chemoreceptors

Summary The coupling of intact natural chemoreceptor structures to potentiometric electrodes results in a new class of electrochemical biosensors with exceptionally fast dynamic response properties and attractive analytical limits. The use of intact sensing structures is advantageous in that both the transduction and conduction functions are contained in the native environment of the neural element. This novel approach is illustrated with antennule structures of the blue crab and characterized in terms of analytical responses to some amino acids.

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Biosensoren auf der Grundlage nativer Chemorezeptoren

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Dedicated to Prof. Dr. W. Fresenius on the occasion of his 75th birthday     

Grafting onto microfibrils of native cellulose

Attempts to modify the surface of oxidized cellulose microfibrils were made using amine terminated molecules. First, native cellulose was oxidized with catalytic amounts of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO), sodium hypochlorite and sodium bromide in water. The primary alcohol moieties were selectively oxidized into carboxyl groups. Then, the oxidized cellulose was coupled with amines derivatives by a peptidic reaction by using carbodiimide and hydroxysuccimide as catalyst and amidation agent. The obtained coupled cellulose showed low polarity, with stability in non-polar solvents. The products were characterized by FTIR, ¹³C NMR, rheology and conductometric titration as well as transmission electron microscopy. Their hydrophobic character was evaluated by observing their behavior in polar and non-polar solvents.     

Isolated single-molecule magnets on native gold

The incorporation of thioether groups in the structure of a Mn12 single-molecule magnet, [Mn12(O12)(L)16(H2O)4] with L = 4-(methylthio)benzoate, is a successful route to the deposition of well-separated clusters on native gold surfaces and to the addressing of individual molecules by scanning tunnelling microscopy.     

Kinetics of immobilized and native invertases

A comparative study has been made of the kinetic characteristics of native invertase and the enzyme immobilized on polyamide in the presence of a substrate (60% sucrose). The thermostability, pH optimum, temperature optimum, the hydrolysis of sucrose, and the dependences of the initial rate of hydrolysis on the concentrations of enzyme and substrate were investigated. It was shown that the covalent addition of invertase to polyamide through glutaraldehyde performed in the presence of 60% sucrose leads to the most stable preparation of the immobilized enzyme.Tashkent Institut of Chemical Technology. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 346–348, May–June, 1998.     

Computational analysis of native and modified oligofructosides

This paper presents a quantum chemical calculation of native (2–7 fructoside residues) and chemically modified (2–4 fructoside residues) levan molecule models. A levan modification was carried out by oxidation and the following reduction or hyrdazonation of the fructoside rings. The conformational particularity and reaction ability was studied for the native and for the modified levan molecules.     

Cellulose nanocrystals from native and mercerized cotton

Cellulose - Nanocelluloses occur under various crystalline forms that are currently being selectively used for a wide variety of high performance materials. In the present study, two cellulose...     

Raman-spectroscopy-based noninvasive microanalysis of native lignin structure

A new robust, noninvasive, Raman microspectroscopic method is introduced to analyze the structure of native lignin. Lignin spectra of poplar, Arabidopsis, and Miscanthus were recovered and structural differences were unambiguously detected. Compositional analysis of 4-coumarate-CoA ligase suppressed transgenic poplar showed that the syringyl-to-guaiacyl ratio decreased by 35% upon the mutation. A cell-specific compositional analysis of basal stems of Arabidopsis showed similar distributions of S and G monolignols in xylary fiber cells and interfascicular cells.     

Fluorescence titration of native and PMS-subtilisin Carlsberg

The effect of pH on the tyrosine and tryptophan fluorescence of both native and phenylmethanesulfonyl (PMS) -subtilisin Carlsberg is studied. The observed transitions in the titration curves at acidic pHs reveal considerable changes in the three-dimensional structure of this enzyme. Conclusions about the conformational stabilities of subtilisin Carlsberg and the homologous protease DY are made.     

Heterodimerization of dye-modified cyclodextrins with native cyclodextrins

The heterodimerization behavior of dye-modified beta-cyclodextrins (1-6) with native cyclodextrins (CDs) was investigated by means of absorption and induced circular dichroism spectroscopy in an aqueous solution. Three types of azo dye-modified beta-CDs (1-3) show different association behaviors, depending on the positional difference and the electronic character of substituent connected to the CD unit in the dye moiety. p-Methyl red-modified beta-CD (1), which has a 4-(dimethylamino)azobenzene moiety connected to the CD unit at the 4' position by an amido linkage, forms an intramolecular self-complex, inserting the dye moiety in its beta-CD cavity. It also associates with the native alpha-CD by inserting the moiety of 1 into the alpha-CD cavity. The association constants for such heterodimerization are 198 M(-1) at pH 1.00 and 305 M(-1) at pH 6.59, which are larger than the association constant of 1 for beta-CD (43 M(-1) at pH 1.00). Methyl red-modified 2, which has the same dye moiety as that for 1 although its substituent position is different from that of 1, does not associate even with alpha-CD due to the stable self-intramolecular complex, in which the dye moiety is deeply included in its own cavity of beta-CD. Alizarin yellow-modified CD (3), which has an azo dye moiety different from that of 1 and 2, caused a slight spectral variation upon addition of alpha-CD, suggesting that the interaction between 3 and alpha-CD is weak. On the other hand, phenolphthalein-modified beta-CD (4), which forms an intermolecular association complex in its higher concentrations, binds with beta-CD with an association constant of 787 M(-1) at pH 10.80, where 4 exists as the dianion monomer in the absence of beta-CD. p-Nitorophenol-modified beta-CDs (5 and 6), each having p-nitorophenol moieties with a different connecting part with an amido and amidophenyl group, respectively, associated with alpha-CD with association constants of 66 and 16 M(-1) for 5 and 6, respectively. The phenyl unit in the connecting part of 6 may prevent the smooth binding with alpha-CD. All these results suggest that the dye-modified CDs, in which the dye part is not tightly included in its CD cavity, associate with the native CD to form heterodimer composed of two different CD units by inserting the dye moiety into the native CD unit. The resulting heterodimers have a cavity that can bind another appending moiety of host molecules. On this basis, more ordered molecular arrays or the supramolecular hereropolymers can be constructed.     

Expanded utility of the native chemical ligation reaction

The post-genomic era heralds a multitude of challenges for chemists and biologists alike, with the study of protein functions at the heart of much research. The elucidation of protein structure, localization, stability, post-translational modifications, and protein interactions will steadily unveil the role of each protein and its associated biological function in the cell. The push to develop new technologies has necessitated the integration of various disciplines in science. Consequently, the role of chemistry has never been so profound in the study of biological processes. By combining the strengths of recombinant DNA technology, protein splicing, organic chemistry, and the chemoselective chemistry of native chemical ligation, various strategies have been successfully developed and applied to chemoselectively label proteins, both in vitro and in live cells, with biotin, fluorescent, and other small molecule probes. The site-specific incorporation of molecular entities with unique chemical functionalities in proteins has many potential applications in chemical and biological studies of proteins. In this article, we highlight recent progress of these strategies in several areas related to proteomics and chemical biology, namely, in vitro and in vivo protein biotinylation, protein microarray technologies for large-scale protein analysis, and live-cell bioimaging.     

Theoretical prediction of the native fluorescence of pharmaceuticals

At present, to search fluorescent compounds or to increase the native fluorescence is an active research line specially and not only with analytical purposes. On some analytical areas and from the early times of applications of fluorescence (mid-fifties) the fluorimeter was defined as the suitable detector for determination of pharmaceuticals and subsequently, this detection mode has been widely applied. Therefore, it is mandatory to develop new strategies to discover or to enhance in a simple way the native fluorescence of organic compounds to increase the number of analytes to be determined by direct fluorescence.In the present paper are studied further applications of a new tool suitable to increase the research in analytical field. Calculations on molecular connectivity and discriminant analysis are applied to a certain number of pharmaceuticals (and some pesticides) on which fluorescence behaviour was observed in an experimental screening or obtained from scientific literature. The screening tests were based on the on-line fluorimetric measurement by using a continuous-flow assembly. The screening comprised pre-selected compounds with different molecular structures. The theoretical predictions agree with the empirical results from the screening test.