bluuebunny/crossref_metadata_2025_split huggingface dataset:
The helix–coil transition in heterogeneous peptides with specific side‐chain interactions: Theory and comparison with CD spectral data
Authors: Gans Paul J. , Lyu Pingchiang C. , Manning Mark C. , Woody Robert W. , Kallenbach Neville R. 
Published: May 2005

AbstractNatural and synthetic peptides that contain detectable intramolecular α‐helical structure in aqueous solution have been used to evaluate the helical propensities for the common amino acids. Experimental spectroscopic data must be fit to a model of the helix–coil transition in order to determine quantitative stability constants for each amino acid. We present here a statistical mechanical description of helix formation in peptides or protein fragments that takes into account multiple internal conformations, heterogeneity in the stabilizing effects of different side chains, and specific side‐chain–side‐chain interactions. The model enables one to calculate values of [θ]222 for a given peptide using the length dependence of the helix signal computed by a quantum mechanical treatment of the nπ* transition that dominates the 222‐nm band. In addition, the helical probability at any residue in the chain is readily computed, and should prove useful as nmr spectral data become available. The free energy of specific side‐chain interactions, including ion pair formation, can be evaluated. Application of the analysis to experimental data on a pair of isomeric peptides, only one of which contains ion pairs, indicates that forming a single glutamate‐lysine ion pair stabilizes the α‐helix by 0.50 kcal/mole in 10 mM sodium ion and pH 7. A survey of the CD data measured for a variety of model peptides is presented, indicating that a single set of s values and σ constant can account for some but not all of the available results.
Transient electric birefringence of two small DNA restriction fragments of the same molecular weight
Authors: Stellwagen Nancy C. 
Published: May 2005

AbstractThe transient electric birefringence of two small DNA restriction fragments of the same molecular weight, one of which migrates anomalously slowly on polyacrylamide gels, has been investigated. Both fragments exhibit negative birefringence. The decay of the birefringence of the anomalously slowly migrating fragment is 8–9% faster than that of the normally migrating fragment. The faster birefringence decay of the anomalous fragment 12A persists under a variety of buffer conditions, suggesting that it is due primarily to static bending and/or curvature of fragment 12A. In reversing electric fields the absolute amplitude of the birefringence of fragments 12A and 12B decreased about 26% before returning to the steady state value. The minimum in the birefringence occurred faster than expected from the birefringence decay times and decreased with increasing electric field strength, suggesting that the minimum is due to a slow polarization of the ion atmosphere. For both fragments, the rise of the birefringence in the Kerr region is about 10% slower than the field‐free decay. The buildup of the negative birefringence is preceded either by an interval when no birefringence is observed or by a small positively birefringent transient, suggesting that a small transverse ionic polarizability is also present. Both DNA fragments exhibit Kerr law behavior over most of the range of electric field strengths investigated. Analysis of the shapes of the saturation curves suggests that differences may exist in the polarization mechanisms of the two fragments.
Conformation of the oligosaccharide receptor for E‐selectin
Authors: Mukhopadhyay Chaitali , Miller Kristine E. , Bush C. Allen 
Published: May 2005

AbstractA tetrasaccharide related to the blood group oligosaccharides, known as sialyl LewisX, has been proposed as the receptor for the lectin responsible for leukocyte adhesion named alternatively as E‐selectin or ELAM‐1. The 13C‐ and 1H‐nmr spectra have been completely assigned for a tetrasaccharide model of this receptor, Neu5Ac α‐(2 → 3)‐Gal β‐(1 → 4)‐[ Fuc α‐(1 → 3)‐] GlcNAc β‐NHAc. Quantitative nuclear Overhauser data (NOESY) have been recorded and analyzed by a complete spin matrix simulation method. Conformational space was exhaustively searched and all conformational models whose simulated NOESY spectra matched the experiment were found. Molecular mechanics and molecular dynamics calculations were carried out to test whether the experimental conformations are low energy and thus likely to represent true single conformations for the tetrasaccharide. It was concluded that while the LewisX trisaccharide portion of the compound adopts a single conformation, there is likely to be some flexibility about the Neu5Ac α‐(2 → 3)‐linkage. A model featuring fast exchange between two different conformations of this linkage is found to be consistent with both the nmr experiments and the molecular dynamics simulations. © 1994 John Wiley & Sons, Inc.
The effect of the L‐azetidine‐2‐carboxylic acid residue on protein conformation. IV. Local substitutions in the collagen triple helix
Authors: Zagari Adriana , Palmer Kathleen A. , Gibson Kenneth D. , Némethy George , Scheraga Harold A. 
Published: May 2005

AbstractThe properties of collagen are affected by the replacement of Pro by imino acid analogues. The structural effect of the low‐level local substitution of L‐azetidine‐2‐carboxylic acid (Aze) has been analyzed by computing the energy of CH3CO‐(Gly‐Pro‐Pro)4‐NHCH3 triple helices in which a single residue of one strand has been replaced by Aze. When Aze is in position Y of a (Gly‐X‐Y) unit, low‐energy local deformations are introduced in the triple helix, i.e., it becomes more flexible. On the other hand, the flexibility of the triple helix is not increased with Aze in position X. The energy of the triple helix to coil transition is not changed significantly by this amount of substitution. In an earlier study, we have demonstrated that the regular substitution of Aze in every tripeptide distorts or destabilizes the triple helix to a large extent [A. Zagari, G. Némethy, & H. A. Scheraga (1990) Biopolymers, Vol. 30, pp. 967–974 ]. Thus, it appears that a high level of substitution is required to cause the observed chemical and biological effects of Aze on collagen. © 1994 John Wiley & Sons, Inc.
The interaction of substituted 2‐phenylquinoline intercalates with poly(A) · poly(U): Classical and threading intercalation modes with RNA
Authors: Zhao Min , Janda Lubomir , Nguyen Johnny , Strekowski Lucjan , Wilson W. David 
Published: May 2005

AbstractThe interaction of a series of 2‐phenylquinoline derivatives with RNA was investigated by means of viscometric, pKa, spectroscopic, binding, Tm, and kinetic methods. Compounds 1,2, and 3 have a piperazyl substituent at the para, meta, or ortho position, respectively, while 4 has an unsubstituted phenyl ring. The pKa results suggest that 1 has three charges, 2 and 3 have more than two charges, and 4 has two charges at pH 6.2. Spectroscopic and Tm results indicate that 1 binds more strongly to RNA than 2–4. Kinetic and modeling results indicate that 1 is a threading intercalator while 2 and 4 are classical intercalators. All experimental results indicate that 3, which has a large twist between the phenyl and quinoline rings, binds weakly with RNA. © 1994 John Wiley & Sons, Inc.
Solitary wave dynamics as a mechanism for explaining the internal motion during microtubule growth
Authors: Chou Kuo‐Chen , Zhang Chun‐Ting , Maggiora G. M. 
Published: May 2005

AbstractMicrotubules, which play many diverse and important roles in biological systems, are usually made up of 13 nearly axial protofilaments formed from individual tubulin molecules. In this paper, a nonlinear dynamic model has been developed to elucidate the mechanism of the internal motion occurring during the assembly of microtubules. The results derived from the model indicate that such internal motion is associated with a solitary wave, or kink, excited by the energy released from the hydrolysis of GTP ⟹ GDP in microtubular solutions. As the kink moves forward, the individual tubulin molecules involved in the kink undergo motions that can be likened to the dislocation of atoms within the crystal lattice. Thus, the dynamic instability of microtubules may be characterized by a series of dislocation motions of the tubulin molecules. An energy estimate shows that a kink in the system possesses about 0.36–0.44 eV, which is quite close to but smaller than the 0.49 eV of energy released from the hydrolysis of GTP. Therefore, the relevant energy derived from our model is fully consistent with experimental observations; this finding also suggests that the hydrolysis energy may be responsible for exciting the solitary wave, or kink, leading to tubulin dislocation in microtubules.Our model, and its intrinsic properties, i.e., dynamic nonlinearity, thermodynamic irreversibility, as well as an energy input from a sustained source, implies that the growth of microtubules is a typical dissipative process and that their structure in vivo is typical of dissipative structures. © 1994 John Wiley & Sons, Inc.
Microbial degradation of asphalt
Authors: Traxler R. W. 
Published: May 2005

AbstractIt would appear from these data that indeed asphalt degradation by bacteria does occur and can be rather rapid under laboratory conditions. The types of bacteria capable of degrading asphalt are diverse. The effects of temperature, pH, and oxygen tension on asphalt degradation are important but not always critical. The optimum conditions vary for different organisms. There are differences in the mechanisms of asphalt assimilation and degradation. There is a specificity of action by different bacteria which most likely involves the chemical components of the asphalts and the enzymatic action of the microorganism.
Mean light intensity—a useful concept in correlating growth rates of dense cultures of microalgae
Authors: Rabe A. E. , Benoit R. J. 
Published: May 2005

AbstractAn analysis of the distribution of light within some culture vessels developed at General Dynamics/Electric Boat is presented. The concept of a mean effective light intensity, Ē, is introduced and procedures are developed for computing Ē for any culture vessel geometry and incident light intensity distribution. A correlation is performed indicating the significance of Ēin assessing the growth rate of dense, continuous cultures of microalagae.
Enzymatic process for mustard seed to produce oil, meal, and allyl isothiocyanate
Authors: Mustakas G. C. , Griffin E. L. , Gastrock E. A. , D'Aquin E. L. , Keating E. J. , Patton E. L. 
Published: May 2005

AbstractRemoval of the pungent factor, allyl isothiocyanate, will partly determine whether mustard seed can become a commerical source for oil and meal in the United States. In processing studies at the Northern Laboratory, the mustard glucoside was converted enzymatically and the pungent oil was removed. This process has now been extended to pilot‐plant scale by using filtration‐extraction equipment at the Southern Laboratory. After desolventization and further steam stripping, the extracted meal had a residual content of 2.9% crude fat and 0.004% allyl isothiocyanate.
Chemical properties of crystalline N‐methylethyloxytetracycline
Authors: Neidleman S. L. , Weisenborn F. L. , Bouchard J. 
Published: May 2005

AbstractThe inclusion of ethionine in Streptomyces rimosus fermentation resulted in the production of N‐methylethyloxytetracycline. The compound has been isolated, crystallized, and a number of its chemical properties determined.
Production of aflatoxin by the culture of strains of Aspergillus flavus‐oryzae on sterilized peanuts
Authors: Codner R. C. , Sargeant K. , Yeo R. 
Published: May 2005

AbstractBy growing Aspergillus parasiticus (C.M.I. 15957) under controlled conditions on sterilized peanuts an average of 265 mg. of aflatoxin per kilogram of peanuts has been produced and subsequently isolated. Other strains from the A. flavus‐oryzae group gave lower yields of aflatoxin and one such strain gave aflatoxin from which certain normal components were absent. The aflatoxin produced on sterilized peanuts by any particular strain of A. flavus‐oryzae was shown by thin‐layer chromatography to contain the same major components as were produced by that strain on unsterilized whole peanuts.
An application of the discrete maximum principle to a stagewise biochemical reactor system
Authors: Fan Liang‐Tseng , Wan Chee‐Gen 
Published: May 2005

AbstractIt is a well‐known fact that choosing a sequence of optimal control variables in each reactor tank of a multistage reactor system can result in a considerable increase of the desired product for a consecutive reaction system. The discrete maximum principle is applied to a generalized optimization problem of first order consecutive biochemical reaction system. A detailed numerical solution as an example is also presented for illustration.
Waste stabilization ponds: Use, function, and biota
Authors: Porges Ralph , Mackenthun Kenneth M. 
Published: May 2005

AbstractStabilization ponds have been widely accepted in recent years, following studies that established deeper understanding of the phenomena associated with the stabilization process. A compilation of information on the use of both sewage and industrial ponds is presented showing types and geographical location in the United States. A total of 1,304 stabilization ponds currently are used as the principal method of sewage treatment serving a population of 2,138,085. Ponds are used for tertiary treatment serving a population of 2,146,951, in 343 instances. Use of 827 industrial ponds by 31 industries in 44 States is also indicated. Indiana ranks first in usage with 159 ponds and Callfornia second with 140. Ponds were classed as effective by 66 percent of the 455 users who reported on this item. Of 149 reports on odors, 73% indicated nuisances. Insect problems were reported in only a small number of instances. Data are presented on design considerations and the mechanism of waste stabilization ponds. Aerobic ponds are given greatest emphasis. Photosynthesis and its dependence upon the algal mass, suitable temperature, incident light penetration, nutrient supply, and induced vertical mixing by wind are of prime importance in the stabilization mechanism. Odors are associated with prolonged anaerobic conditions, and these may persist up to 4 weeks following extended ice cover in cold climates, if BOD loadings are 25 lbs. per acre per day or greater. Nitrogen and carbon may be limiting factors in the development of an algal mass. Coliform, BOD, and nutrient removals are presented for various physical, chemical, and climatic conditions. Although fecal streptococci removal averaged 97% in a study pond, they were still discharged in the effluent at a rate of 700,000 per second in winter and 70,000 per second in summer. A striking similarity exists generally among the algal speciation in stabilization ponds, regardless of geographic location. The algal mass is, however, dependent upon unique pond conditions and location, and may vary upwards to nearly 5 million algal cells per milliliter, 34,000 p.p.m. by volume, or 30–35 tons per acre per year. The problem of blue‐green algal mats and resultant pigpen odors in extremely localized areas is duscussed. Midges and midge larvae may have an impact on the nutrient cycle in a stabilization pond, and may pose a potential localized nuisance in some areas. Mosquito problems have usually been associated with growth of aquatic vegetation. Suggestions for minimizing the potential problem are discussed.
Decomposition of organic wastes by Sphaerotilus
Authors: Pipes W. O. , Jones P. H. 
Published: May 2005

AbstractSphaerotilus is usually present in biological waste treatment processes and is considered to be a nuisance organism because it may cause bulking of activated sludge. However, it may play an important role in the decomposition of putrescible organic matter in properly operated biological waste treatment processes. The research described herein is a study of the variety of types of organic compounds which may be decomposed by Sphaerotilus and the effect of some environmental factors upon the rate of decomposition. Although there are some types of compounds which cannot be decomposed by Sphaerotilus, it is shown that this organism is able to assimilate and oxidize a large variety of organic compounds and that it is tolerant of an extremely wide range of environmental conditions. The role of Sphaerotilus in biological waste treatment is discussed in the light of the data presented.
Studies on the removal of alkyl benzene sulfonate by microorganisms
Authors: Hartmann Ludwig 
Published: May 2005

AbstractThese experiments show that ABS can be adsorbed and desorbed from microbial cell surfaces. The adsorption equilibria between the free and adsorbed phases are primarily influenced by the pH of the system. The effects of ABS upon the biochemical activities of bacteria depended upon the amount of ABS adsorbed and the type of bacteria present. The behaviour of ABS is essentially the same whether in the presence of pure or mixed bacterial cultures. Two desorption experiments with soil from a reclaimed water spreading basin which has received sewage over a six month period showed that at least 82% of the ABS “loss” was recoverable from the soil. In all the experiments carried out in this study no evidence was obtained for the biochemical degradation of ABS.
Biodegradation of anionic and nonionic surfactants under aerobic and anaerobic conditions
Authors: Wayman C. H. , Robertson J. B. 
Published: May 2005

AbstractBecause branched‐chain alkyl benzene sulfonate (ABS) is well known to create water pollution problems in surface water and ground water, a study was made on the biodegradation of this surfactant along with other anionic and nonionic surfactants in detergents by water bacteria. Biodegradation was evaluated by the conventional river die‐away test employing the methylene‐blue method or surface‐tension techniques as analytical tools. Under anaerobic conditions, sugar detergents (sucrose esters) seem to be an ultimate solution to water problems created by branched‐chain ABS; in aerated water, straight‐chain ABS, sulfo tallow methyl esters, and nonionic surfactants are preferable to branched‐chain ABS to improve water problems.
A method of automatic pH control of a bicarbonate‐CO2 buffer system for the submerged culture of hamster kidney cells
Authors: Telling R. C. , Stone C. J. 
Published: May 2005

AbstractThe equipment and operational techniques are described which were found suitable to control pH in the range 6.8–7.8 pH, within ±0.03 pH units of the desired value, at cell concentrations up to a maximum of 2.5 × 106/ml. The results of batch growth of a suspension strain of the BHK cell (clone 13) under conditions of controlled pH are given and the significance of these results is discussed.
Rapid estimation of 1‐dehydro‐17‐α‐methyltestosterone produced by microbiological oxidation of 17‐α‐methyltestosterone
Authors: Mizsei Antal , Szabó Antal 
Published: May 2005

AbstractA method has been devised for the estimation in fermentation media, of 1‐dehydro‐17‐α‐methyltestosterone in the presence of 17‐α‐methyltestosterone. This method involves the extraction of the steroids with chloroform, and spectrophotometric measurement of the chromogen formed by a specific color reaction with sulfuric acid and 1‐dehydro‐17‐α‐methyltestosterone. The fermentation liquor and 17‐α‐methyltestosterone do not interfere. With this rapid (30 min.) method, quantitative tests on the progress of the steroid transformation can be made at frequent intervals during one fermentation run, these tests yielding the necessary information for an adequate control of the optimum conditions of production.
Problems of design and ecological considerations in mass culture of algae
Authors: Mayer A. M. , Zuri U. , Shain Y. , Ginzburg H. 
Published: May 2005

AbstractA 2000 l. 1 m. deep mass culture of algae was operated with continuous stirring, as an open system. The system behaved as an ecological unit selecting the most favored species. The ecological conditions could be modified by stirring speed and pattern in the tank. Methods for improving yields and utilization of CO2 are described. Assessment of algal species for suitability in mass cultures is discussed. Yields obtained were 13 g. dry matter/sq. m. illuminated area/day.
Some experiments on the disintegration of yeast by high intensity ultrasound
Authors: Neppiras E. A. , Hughes D. E. 
Published: May 2005

AbstractThe effects of ambient pressure and ultrasonic power on the disintegration of yeast suspension have been investigated. The results obtained are, in the main, consistent with the theory that cell breakage is primarily a phenomenon dependent on producing gaseous cavitation in the medium. The importance of the experimental results and techniques applied to Commercial cell disintegrators is briefly discussed. A simple flow system is described which is easily attached to probe‐type disintegrators. The use of a crystal pickup for tuning and control purposes is described.
The “Bilthoven unit” for submerged cultivation of microorganisms
Authors: van Hemert Paul 
Published: May 2005

AbstractA unit of four fermentors, which is specially designed for batch and continuous cultivation of pathogenic microorganisms in vaccine preparation, is described. Each unit consists of a panel with controls and recorders. The fermentor itself consists of a stainless steel lid, to which a spherical or cylindrical glass vessel is attached. Holding volumes are from 1 to 100 l. (3 and 7 l. being mostly used) and can be obtained by simply exchanging the vessels which have similar flanges.Interchangeability, not only of the glass vessels, but also of the stirrers, pipes, pH electrodes, etc., together with variable control of temperature, stirrer speed, air or gas flow, and pH value gives the unit a maximum of versatility.
Effect of pressure on the α‐amylase catalyzed hydrolysis of starch
Authors: Griskey Richard G. , Richter Thomas 
Published: May 2005

AbstractIt was found that moderate pressures (16.0 to 43.1 atmospheres) perceptibly decreased the rate of α‐amylase catalyzed starch hydrolysis. The decreased rate was apparently due to pressure induced deactivation of the enzyme.
Steam corrosion and steam corrosion inhibition in autoclave sterilization of dental and surgical steel materials
Authors: Holmlund Lars G. 
Published: May 2005

AbstractSteam corrosion and steam corrosion inhibition of dental and surgical instrument materials during autoclave sterilization have been investigated. The corrosion tests were performed on carbon steel test samples and on round dental burrs. Cyclohexylamine or decylamine were used as corrosion inhibitors, added to the “feed water,” i.e., deionized water, to a concentration of 0.1%. Before the corrosion experiment the surfaces of the test materials were standardized and calibrated by means of ultrasonic treatment. After the experiment the corrosion products were removed from the test samples or burrs using the same ultrasonic cleaning. Deionized water was used as cleaning liquid, and was then analyzed for the amount of Fe dissolved. The amount of corrosion was expressed as μg. Fe/cm.2 sample surface area or μg. Fe/burr. The results show that considerable corrosion occurs when carbon steels are exposed to steam during autoclaving, but if cyclohexylamine or decylamine is added to the steam under the otherwise unchanged experimental conditions the total corrosion was reduced by 96–99%. No cytotoxic effect on HeLa cells could be detected with surface products possibly containing traces of amine and/or amine salts—nor with corrosion products alone—when these products were removed from the test materials by means of ultrasonic cleaning.