bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of folding and unfolding of ββ‐tropomyosin
Authors: Mo Jianming , Holtzer Marilyn Emerson , Holtzer Alfred
Published: December 2004

The kinetics of folding from random coils to two‐chain coiled coils of ββ‐tropomyosin was studied by stopped‐flow CD (SFCD) in the backbone region (222 nm). Two species were studied: the reduced form and the doubly disulfide cross‐linked form. The proteins were totally unfolded in 6M urea‐saline buffer, then refolded by tenfold dilution into benign k buffer. In the refolding medium, they spontaneously recover the two‐chain coiled‐coil structure. Reduced ββ refolds in at least two stages: one or more fast phases (<0.04 s), in which an intermediate with 71% of the equilibrium ellipticity forms, followed by a slower time‐resolvable phase that completes the folding. The slow phase is first order, signifying that dimerization occurs in the fast phase. The time constant of the slow phase is 2 s at 20°C and requires activation parameters of ΔS≠ = –7 ± 0.3 cal/mol · K, ΔH≠ = 15 ± 1 kcal/ mol. These results are very similar to those previously found for the reduced genetic variant αα‐tropomyosin. In contrast, refolding of doubly disulfide cross‐linked ββ is complete within the dead time (< 0.04 s), whereas the singly cross‐linked αα species also displays a slow phase. The opposite process, unfolding reduced ββ from the coiled‐coil state, is complete within the dead time, as in the αα variant.
Solution conformations of two flexible cyclic pentapeptides: cyclo(Gly‐Pro‐D‐Phe‐Gly‐Ala) and cyclo(Gly‐Pro‐D‐Phe‐Gly‐Val)
Authors: Stroup Adam N. , Rockwell Arlene L , Gierasch Lila M.
Published: December 2004

In an effort to explore the residue preferences in three‐residue reverse turns (so‐called ‐γ‐turns), two cyclic pentapeptides—cyclo(Gly1‐Pro2‐D‐Phe3‐Gly4‐Ala5) (I) and cyclo (Gly1‐Pro2‐D‐Phe3‐Gly4‐Val5) (II)—have been synthesized and analyzed by nmr. It was anticipated that the Gly‐Pro‐D‐Phe‐Gly portions of these molecules would favor a β‐turn conformation, leaving the remainder of the molecule to adopt a γ turn, as seen in several previously studied model cyclic pentapeptides. The nmr data for both peptides in CDCl3 (5% DMSO‐d6) and in neat DMSO‐d6 indicate that the most populated conformation contains a distorted β turn around Pro2‐D‐Phe3, which includes a γ turn around D‐Phe3. The distorsion in the β turn does not impede the formation of an inverse γ turn around residue 5, and indeed, this conformation is observed in both peptides. Both the alanine and the bulkier valine residues are therefore found to be compatible with an inverse γ turn. Molecular dynamics simulations on the title peptides are reported in the following paper. These simulations indicate that there is conformational flexibility around the D‐Phe3‐Gly4 peptide bond, which enables the formation of the γ turn around D‐Phe3. The third paper in this series explores the impact of a micellar environment on conformational equilibria in II. © 1992 John Wiley & Sons, Inc.
Hydrational and intrinsic compressibilities of globular proteins
Authors: Kharakoz D. P. , Sarvazyan A. P.
Published: December 2004

Partial compressibilities of globular proteins in water are reviewed. Contribution of hydrational and of intrinsic compressibilities to experimental partial quantity have been evaluated from ultrasonic data using two independent methods: (a) additive calculation of the hydrational contributions of the surface atomic groups and (b) an analysis of correlation between partial compressibility and molecular surface area. The value (14 ± 3) × 10−6 bar −1 for the isothermal compressibility coefficient of the protein interior at 25°C was obtained as an average value for variety of globular proteins. This value is similar to that of solid organic polymers. Possible relaxation contribution to partial compressibility is roughly estimated from comparison of thermodynamic with x‐ray data on protein compressibility. The average compressibility of water in the hydration shell of proteins was found to be 35 × 10−6 bar −1, which is 20% less than that of pure water. © 1993 John Wiley & Sons, Inc.
Calcium‐dependence of laminin binding to phospholipid membranes
Authors: Ramsden Jeremy J.
Published: December 2004

Laminin is the most abundant noncollagenous protein in basement membranes. Its selfassembly has been studied in solution, and it has been established that calcium ions induce partially reversible aggregation. The behavior at a lipid membrane surface is of greater biological significance, but it is difficult to study quantitatively binding kinetics at a surface. The present work uses a powerful new integrated optics technique to measure the absorption and aggregation of the laminin–nidogen at a bilayer lipid membrane surface. It is found that the binding of a single layer of laminin at the lipid membrane is independent of the presence of calcium, but that the building up of multilayer laminin membranes requires calcium, and that these may not be destroyed by a calcium‐complexing agent. © 1993 John Wiley & Sons, Inc.
1H, 13C, and 15N assignments and secondary structure of the FK506 binding protein when bound to ascomycin
Authors: Xu Robert X. , Nettesheim David , Olejniczak Edward T. , Meadows Robert , Gemmecker Gerd , Fesik Stephen W.
Published: December 2004

The 1H, 13C, and 15N resonances of FKBP when bound to the immunosuppressant, ascomycin, were assigned using a computer‐aided analysis of heteronuclear double and triple resonance three‐dimensional nmr spectra of [U‐15N] FKBP/ascomycin and [U‐15N, 13C] FKBP/ascomycin. In addition, from a preliminary analysis of two heteronuclear four‐dimensional data sets, 3J coupling constants, amide exchange data, and the differences between the Cα and Cβ chemical shifts of FKBP to random coil values, the secondary structure of FKBP when bound to ascomycin was determined. The secondary structure of FKBP when bound to ascomycin in solution closely resembled the x‐ray structure of the FKBP/FK506 complex but differed in some aspects from the structure of uncomplexed FKBP in solution. © 1993 John Wiley & Sons, Inc.
IR study of the proton acceptor ability of N‐t‐butoxycarbonylproline N′‐methylamide
Authors: Parmentier J. , De Wael K. , Samyn C. , Zeegers‐Huyskens Th.
Published: December 2004

Hydrogen bonding between N‐t‐butoxycarbonylproline N′‐methylamide and phenol derivatives (pKa = 10.20–7.75) are investigated by ir and Fourier transform ir spectrometry. The thermodynamic parameters determined in carbon tetrachloride solution show that the complexes are of medium strength, the stability constants at 298 K range from 80 to 1530 L mol−1, and the enthalpies of complex formation range from – 30 to –34 kJ mol−1. The study of the ir spectra in the νOH, νNH, and νco regions shows that complex formation occurs at the oxygen atom of the amide carbonyl. Hydrogen‐bond formation at this site strengthens the intramolecular hydrogen bond of the seven‐membered ring. © 1993 John Wiley & Sons, Inc.
Molecular dynamics of sickle and normal hemoglobins
Authors: Prabhakaran M. , Johnson Michael E.
Published: December 2004

Molecular dynamics (MD) simulations have been carried out for 62.5 ps on crystal structures of deoxy sickle cell hemoglobin (HbS) and normal deoxy hemoglobin (HbA) using the CHARMM MD algorithm, with a time step of 0.001 ps. In the trajectory analysis of the 12.5–62.5 (50 ps) simulation, oscillations of the radius of gyration and solvent‐accessible surface area were calculated. HbS exhibited a general contraction during the simulation, while HbA exhibited a nearly constant size. The average deviations of simulated structures from the starting structures were found to be 1.8 Å for HbA and 2.3 Å for HbS. The average rms amplitudes of atomic motions (atomic flexibility) were about 0.7 Å for HbA and about 1.0 Å for HbS. The amplitudes of backbone motion correlate well with temperature factors derived from x‐ray crystallography. A comparison of flexibility between the α‐ and β‐chains in both HbA and HbS indicates that the β‐chains generally exhibited greater flexibility than the α‐chains, and that the HbS β‐chains exhibit greater flexibility in the N‐terminal and D‐ and F‐helix regions than do those of HbA. The average amplitude of backbone torsional oscillations was about 9°, a value comparable with that of other simulations, with enhanced torsional oscillation occurring primarily at the ends of helices or in loop regions between helices. Comparison of atomic flexibility and torsional oscillation results suggests that the increased β‐chain flexibility results from relatively concerted motions of secondary structure elements. The increased flexibility may play an important role in HbS polymerization. Time course analysis of conformational energy of association, hydrogen bonding and hydrophobic bonding (as calculated from solvent accessibility) shows that all three of these factors contribute to the stability of subunit association for both hemoglobins. © 1993 John Wiley & Sons, Inc.
Specific helix stabilization of poly(L‐glutamic acid) in mixed counterion systems
Authors: Satoh Mitsuru , Kato Fusaaki , Komiyama Jiro
Published: December 2004

The coil–helix transitions of poly (L‐glutamic acid) in aqueous alcohol solutions have been investigated for mixed counterion systems. It has been found that coexistence of two kinds of counterion species, i.e., two alkali metal counterions, alkali and alkaline earth metal, and two alkaline earth metals, specifically stabilizes or destabilizes the helix conformation depending upon the combination of the counterion species. The most striking enhancement of the helix content was observed for the combination of Li+ and K+ counterions. It has been suggested that the helix stabilization is attributed to the reduction of the free energy in the contact ion pair formation between the polymer charges and the counterions in the mixed counterion systems. © 1993 John Wiley & Sons, Inc.
Crystal state conformation of three azapeptides containing the Azaproline residue, a β‐turn regulator
Authors: Lecoq A. , Boussard G. , Marraud M. , Aubry A.
Published: December 2004

The molecular structure of three protected AzaPro‐containing peptides have been determined by x‐ray diffraction: Z‐AzaPro‐NHiPr (1; Z: benzyloxycarbonyl), Z‐AzaPro‐L‐Ala‐NHiPr (2), and Boc‐L‐Ala‐AzaPro‐NHiPr (3; Boc: tert‐butyloxycarbonyl). Starting from the key synthon benzyl‐azaprolinate, compounds 1, 2, and 3 have been prepared by combined use of liquid phase peptide synthesis method and adequate isocyanates. In all peptides, the following geometric characteristics are retained: (a) pyramidal character of the two nitrogen atoms of the pyrazolidine ring; (b) pseudo cis conformation of the urethane (1, 2) or tertiary amide (3) function preceding the AzaPro residue; (c) identical absolute values of the Azaproline residue torsion angles “ϕ, ψ” respectively 111° and 23°. In compound 2, the two nitrogen atoms of the pyrazolidine ring are R, R but the opposite S, S absolute configurations are observed in compound 3. In the crystal, compound 3 adopts a folded structure similar to a type VI β‐turn with a weak intramolecular i + 3 → i hydrogen bond, while an extended structure is observed in compound 2. In the light of our findings, in a peptide chain and contrary to the Pro residue, an AzaPro residue should prevent the formation of any type of any type of β‐turn with the residue following it but could accommodate a folded structure with a pseudo type VI βturn with the preceding residue. If confirmed, this would be of tremendous importance in the design of biologically active peptides and drugs. © 1993 John Wiley & Sons, Inc.
Structures of peptides from α‐amino acids methylated at the α‐carbon,
Authors: Toniolo C. , Crisma M. , Formaggio F. , Valle C. , Cavicchioni G. , Precigoux G. , Aubry A. , Kamphuis J.
Published: December 2004

The structural preferences of peptides (and depsipeptides) from the achiral MeAib and Hib residues, and the chiral Iva, (αMe) Val, (αMe) Leu, and (αMe) Phe residues, as determined by conformational energy computations, x‐ray diffraction analyses, and 1H‐nmr and spectroscopic studies, are reviewed and compared with literature data on Aib‐containing peptides. The results obtained indicate that helical structures are preferentially adopted by peptides rich in these α‐amino acids methylated at the α‐carbon. Intriguing experimental findings on the impact of the chirality of Iva, (αMe) Val, and (αMe) Phe residues on helix screw sense are illustrated. © 1993 John Wiley & Sons, Inc.
Conformational and topographical considerations in the design of biologically active peptides
Authors: Hruby Victor J.
Published: December 2004

An outline of the basic considerations that are under development for the rational design of biologically active peptides and peptidomimetics is given. The necessary interplay of biophysical, chemical, and biological considerations is emphasized. The importance of properly designed biological assays to provide chemical information analogous to that from biophysical studies is discussed. The development of asymmetric synthesis in conjunction with conformational considerations for the preparation of specialized amino acids and amino acid mimetics is a critical aspect of the approach. The overall approach is illustrated with three examples from our laboratory: (1) the redesign of somatostatin to a highly potent and selective μ‐opioid receptor antagonist using conformational and topographical considerations in design and for obtaining insights into the pharmacophor; (2) the use of topographical considerations for obtaining oxytocin antagonists; and (3) the application of designer amino acids prepared by asymmetric synthesis to obtain insight into the topographical requirements at δ‐opioid receptors. © 1993 John Wiley & Sons, Inc.
Conformational mobility in cyclic oligopeptides
Authors: Kopple Kenneth D. , Bean John W. , Bhandary Krishna K. , Briand Jacques , D'Ambrosio Cynthia A. , Peishoff Catherine E.
Published: December 2004

Analysis of two isomeric cyclic hexapeptides of composition (Asp, Arg, Gly2, Pro, D‐Pro) by a nuclear Overhauser effect constrained distance geometry conformation search yielded a narrowly defined backbone conformation for one and considerable ambiguity about the conformation in part of the other. Preliminary 13C relaxation studies of these peptides suggest that it is possible that this difference may correspond to a physical difference in internal mobility. In connection with this observation, other experimental evidence bearing on the backbone conformational mobility of cyclic oligopeptides with 4–10 residues, frequently considered to have well‐defined backbones, is reviewed. Conformational heterogeneity involving rotation of a peptide bond plane relative to the overall ring plane is identified as a common phenomenon. Nuclear magnetic resonance line‐shape studies at temperatures down to 200 K can detect backbone motions with activation free energy barriers down to about 10 kcal/mole, but conformational exchange with lower barriers, though detectable in other ways, will not be obvious from nmr spectra alone. © 1993 John Wiley & Sons, Inc.
Hydrophobicity and stability for a family of model proteins
Authors: Muller Norbert
Published: December 2004

According to the conventional definition, the hydrophobic effect is a result of thermodynamic changes occurring when a nonpolar group dissolves in water and attributable to the fact that water in contact with such a group has special structural and energetic properties. Disagreement now exists as to whether this effect promotes or hinders protein denaturation. Taking the heat capacity change of unfolding as a measure of the hydrophobicity of the protein interior, others have shown that protein stabilities are systematically affected by changes in hydrophobicity. It has been suggested that the observed trends show that hydrophobic hydration is intrinsically a destabilizing factor. Model calculations using known equations for the stability curves and certain simplifying assumptions now show that such regularities provide no evidence for or against this conclusion. All available data can be rationalized if hydrophobic terms are evaluated from models that require a positive hydrophobic contribution to the Gibbs energy of unfolding. The calculations also confirm the recent finding that any set of proteins with denaturation temperatures between about 330 and 380 K that exhibits entropy convergence at about 386 K is thermodynamically required to show enthalpy convergence at approximately the same temperature. © 1993 John Wiley & Sons, Inc.
Effect of cationic drugs on suprahelical organization of DNA
Authors: Krishna K. Gopala , Kumar T. K. Suresh , Pandit M. W.
Published: December 2004

Interaction of a minor groove‐binding drug Hoechst‐33258, and an intercalating drug, proflavin, with the PSI (+) form of DNA, was studied using CD spectroscopy. Both drugs are shown to relax the suprahelical organization of DNA, leading to the formation of a B‐like structure, above a certain drug to phosphate ratio. However, unlike proflavin, Hoechst‐33258 brings about further structural changes after formation of the B‐like structure whereas proflavin does not. A reversal of the CD signal in the 300–450‐nm spectral region is also observed with Hoechst‐33258, indicating a change in the handedness of the suprahelical organization of DNA. To the best of our knowledge, drug‐mediated changes as presented in this paper have not been reported so far. © 1993 John Wiley & Sons, Inc.
Intramolecular interference effects in dynamic light scattering from rigid rings
Authors: Gebe John A. , Schurr J. Michael
Published: December 2004

A formula for the apparent diffusion coefficient [Dapp(κ)] of a rigid ring is derived from the exact first cumulant of its dynamic structure factor. Dapp(κ) is expressed in terms of the ring radius, the diffusion coefficients (Dzz and Dxx) for translation parallel and perpendicular, respectively, to the symmetry axis, and the diffusion coefficients (D and D) for rotation around the symmetry and transverse axes, respectively. Dapp(κ) exhibits oscillations as a function of the scattering vector k, which depend on D and the anisotropy of translational diffusion (Dzz − Dxx). The maxima in Dapp(κ) are associated with minima in the static structure factor S(κ, 0), which are due to destructive intramolecular interference. The oscillations in Dapp(κ) result from periodic variations in the relative intensities of scattered light from different orientations of the ring, which manifest the various motions to different extents. The orientations contributing most to the scattered intensity are those that exhibit the least destructive interference and consequently contribute most to the decay of the dynamic structure factor. © 1993 John Wiley & Sons, Inc.
Low oxygen affinity derivatives of human hemoglobin by fixation of polycarboxylic dextran to the oxyform
Authors: Prouchayret F. , Dellacherie E.
Published: December 2004

Solutions of modified adult human hemoglobin (Hb) have potential applications as physiological oxygen carriers. The chemical modification that has been the most studied during the last few years is the cross‐linking of the protein between its two αβ dimers, in order, first, to hamper their diffusion through the kidney and therefore increase the plasma persistence of Hb, and second, to decrease its oxygen affinity. However, despite the cross‐linking, the vascular retention time is only increased by a factor of three, and a supplementary modification of cross‐linked Hb is needed in order to further improve its in vivo half‐life. The Hb derivatives described in this paper were obtained by the covalent fixation of benzene tetracarboxylate‐substituted dextran onto oxyHb. The resulting conjugates all exhibited a higher P50 than native Hb. The experiments carried out in the presence of inositolhexaphosphate showed that the allosteric sites of Hb molecules were occupied by the polymeric reagent. The important decrease in the Bohr effect and the lack of the Cl− effect on the oxygen‐binding properties proved that the Val 1α residue was also substituted. Finally, the ability of some conjugates to unload as much O2 as blood, together with their other properties, make them quite promising candidates as red cell substitutes. © 1993 John Wiley & Sons, Inc.
The influence of hydration on the conformation of bovine serum albumin studied by solid‐state 13C‐nmr spectroscopy
Authors: Gregory Roger B. , Gangoda Mahinda , Gilpin R. K. , Su Wen
Published: December 2004

13C proton‐decoupled cross‐polarization magic‐angle spinning nmr spectra of bovine serum albumin are reported as a function of hydration. Increases in hydration level enhance the resolution of the peak centered at about 40 ppm but has little or no effect on the other spectral peaks. Hydration has little effect on either the rotating frame proton spin–lattice relaxation time or the cross‐relaxation time for any of the peaks, suggesting that the efficiency of dipolar coupling is largely preserved on hydration of the protein. Resolution enhancement of the peak at 40 ppm is not understood, but possible sources of the behavior include a decrease in the line width of contributing resonances from lysine ε carbons due to increased motional averaging on hydration, reordering of disulfide bridges, and titration shifts induced by hydration. Hydration of bovine serum albumin appears to have little effect on the distribution of conformations sampled by the protein so that the broad distribution of conformations observed in the dry state is also observed in the fully hydrated state. This is in contrast to lysozyme where significant ordering of the conformation is seen on hydration. © 1993 John Wiley & Sons, Inc.
Synthesis and biological activity of tripeptide FR113680 analogues containing unconventional amino acids
Authors: Caliendo G. , Calignano A. , Grieco P. , Mancuso F. , Perisutti E. , Santini A. , Santagada V.
Published: December 2004

In order to further develop structure–activity relationships and to get information about the biological active conformations we synthetized analogues tripeptide to the FR 113680 [Ac‐ Thr‐D‐Trp(CHO)‐PheNMeBzl; Ac: acethyl], in which the phenylalanine residue was replaced by unconventional amino acids [1,2,3,4‐tetrahydroisoquinoline‐3‐carboxylic acid (Tic); (3aS, 7aS)‐octahydroindole‐2‐carboxylic acid (Oic); (S,S,S)‐2‐azabiciclo[3.3.0]octane‐3‐carboxylic acid (Aoc); 3‐(1′‐naphthyl) alanine (Nap) phenylglicine (Phg); thienylalanine (Thi)]. The biological activity of the peptides was performed on guinea pig ileumfar neurokinin 1 (NK‐1) and on rat colon for neurokinin 2 (NK‐2). In particular, the replacement of the Phe3 by the Oic (8a) gave an higher antagonist activity in both NK‐1 and NK‐2 receptors, but no improvement in selectivity with respect to reference tripeptide (FR113680) The compound (8a) represent the first example of highly potent peptides that do not contain an aromatic mi no acid of the third position as had been previously considered essential. © 1995 John Wiley & Sons, Inc.
Conformation and dynamics of dimeric ureido‐balhimycin
Authors: Eberstadt Matthias , Guba Wolfgang , Kessler Horst , Kogler Herbert , Mierke Dale F.
Published: December 2004

The conformation of the antibiotic ureido‐balhimycin has been investigated by proton nmr and refined with computer simulations. The dimeric structure cj ureido‐balhimycin was established by unambiguous identification of 6 nuclear Overhauser effects (NOEs) as intermonomeric, out of the total of 186 NOEs observed. Via distance geometry calculations the antiparallel orientation of the two monomers was demonstrated. Further refinement by molecular dynamics simulations provided the essential hydrogen bonds and aromatic interactions responsible for interfacial stabilization. The computational protocol illustrated here (distance geometry to define the coarse topology and molecular dynamics for refinement) should find general applicability in the study of homodimers. © 1995 John Wiley & Sons, Inc.
Submerged citric acid fermentation of ferrocyanide‐treated cane molasses
Authors: Clark D. S.
Published: December 2004

Ferrocyanide‐treated cane molasses was fermented in 2.5‐l. Pyrex tower fermenters using pellets of Aspergillus niger, grown in beet molasses, as an inoculum. The success of the process depended on accurate control of the ferrocyanide concentration in the fermentation mash. Highest yields (up to 80% conversion of available sugar in 8 days) were obtained when the ferrocyanide concentration was 20 p.p.m. at the start of fermentation and then increased to 80–150 p.p.m. at the 24‐hr. period. Addition of phosphate, nitrate, or methanol to fermentation mash did not increase rate of acid production or final yield.
Use of ethylene glycol in counter flow electrophoresis and in cold concentration of DNA and protein solutions
Authors: Eliasson R. , Hammarsten E. , Lindahl T.
Published: December 2004

Counter flow electrophoresis was adapted for temperatures down to −5°C. by the use of ethylene glycol. A method is described for evaporation of water solutions containing ethylene glycol at temperatures between −5 and −10°iC. without ice formation. These measures were found not to affect the transforming activity (two markers) of Bacillus subtilis DNA.
Carbon balance in high rate dissimilation of acetic acid in semicontinuous methane fermentation
Authors: Ghose T. K. , Gupta B. Das , Bhattacharyya B. C.
Published: December 2004

The nature of anaerobic methane fermentation has been studied extensively over a period of about three years by means of 10‐l. semicontinuous fermenters, with ethyl alcohol and calcium acetate as carbon and energy sources. The inoculum for the two systems was isolated by enrichment techniques from primary sewage sludge and used to initiate the processes. No subsequent seeding was necessary. The fermentation was started with a substrate carbon concentration of 50 mmole/l. which was gradually increased to 400 mmole/l.; this means that an increase of substrate level from 3000 ppm to 24,000 ppm of acetate and from 2300 to 18400 ppm of alcohol medium were effected during the study. Such high acetate tolerance of the methane organism does not appear to have been reported before; it was the results of adaptation by the organisms in a semicontinuous culture for a period of 30 months. Effect of supplementary available nitrogen on the rate of gas production at different carbon levels (acetate) was also studied. It was found from the gas analyses that CH4: CO2 ratios were always more than 2 to 3 times the theoretical values, when acetate was used as substrate carbon. At some stages of acetate breakdown the concentration of hydrogen in the gaseous products was found to be as high as 8–9%, a very significant feature of this fermentation. Although sulphate ions were carefully excluded from the constitutents of the media (Analytical reagent chemicals and double‐distilled water used throughout) during the period of study (30 months), contaminants later identified as Desulphovibrio desulphuricans were found throughout the study. Morphological study of the organisms reveal that they are short rods appearing in individual or chain form, highly motile, gram‐positive and nonflagellated, similar to Methanobacterium söhngenii Barker.
Fermentation of long‐chain compounds by Torulopsis magnoliae. II. Factors influencing production of hydroxy fatty acid glycosides
Authors: Spencer J. F. T. , Tulloch A. P. , Gorin P. A. J.
Published: December 2004

A strain of Torulopsis magnoliae, an osmophilic yeast isolated from flowers, produced an extracellular hydroxy fatty acid glycoside of sophorose which was easily recoverable as a heavier‐than‐water “oil”. The yield of this product was greatly increased and the nature of the hydroxy fatty acid portion of the molecule was modified, within limits, by the addition of fatty acid esters, hydrocarbons, or glycerides. Yields of hydroxy fatty acids of up to 90% of the substrate added were achieved. Commercially available substrates such as tall oil fatty acids, molasses, and corn steep liquor could be used. Good aeration was necessary, and control of the concentration of nitrogenous substrates and of temperature improved the yields.
Mass cultivation of algae in pure heavy water
Authors: Daboll Homer F. , Crespi Henry L. , Katz Joseph J.
Published: December 2004

Strains of the green algae Scenedesmus obliquus, Chlorella vulgaris, and C. pyrenoidosa 7‐11‐05, and of the blue‐green algae Fremyella diplosiphon, Plectonema calothricoides, Phormidium luridum, and Synechococcus lividus have been mass cultured autotrophically in essentially pure D2O. Closed Lucite rocking‐box units containing 5 liters of culture media can produce 1 to 2 g. (dry weight) per day of fully deuteriated algae or of fully deuteriated, fully 15N‐substituted algae. Racks for six such culture units are readily constructed from commerically available parts. Operation has been routine and essentially trouble‐free. The algae produced have proved to be an excellent source of completely isotopically substituted metabolites.
“Sleeve” stirrer for submerged cultures
Authors: Schultz J. S. , Melnykovych G.
Published: December 2004

An aseptic agitation system for submerged culture has been devised. It consists of a stirring rod which is isolated from the interior of the culture vessel by a sleeve of flexible plastic tubing.
Oil cake meal for preparation of protein hydrolysate
Authors: Murti C. R. Krishna
Published: December 2004

With a view to preparing substitutes for liver or other animal protein hydrolysates used in the treatment of protein malnutrition, a process has been developed based on sesame and mustard cakes as the starting materials. The laboratory process has been successfully scaled up to pilot plant production to compute tentative costing schedule. Essentially the process consists in defatting the cake, isolating the protein by peptization and isoelectric precipitation, enzymatically digesting the protein isolate by papain, and concentrating the digest under reduced pressure. The final product is a light brown fluffy powder, rich in almost all the essential amino acids. Growth experiments with rats have indicated that the product is comparable to commercial casein although supplementation with lysine could further enhance its biological value.
Extraction and separation of nucleotides from Escherichia coli
Authors: Lilly M. D.
Published: December 2004

A laboratory process for the isolation of acid soluble nucleotides from bacteria has been scaled‐up. Escherichia coli was grown in 220‐l. batches, harvested by centrifugation, and extracted with cold trichloracetic acid. The nucleotides in the extract were separated by adsorption onto a Dowex‐1 ion exchange resin column followed by elution with dilute hydrochloric acid and lithium chloride. After concentration of the effluent, the lithium chloride was removed by extraction with organic solvents. The overall yield of nucleotides was 75–80%. This elution system has also been used for the separation of nucleotides from bakers' yeast extracts.
Studies on automatically aerated biosynthetic processes. I. The effect of agitation and CO2 on penicillin formation in automatically aerated liquid cultures
Authors: Nyiri L. , Lengyel Z. L.
Published: December 2004

The oxygen demand of Penicillium chrysogenum culture was supplied by an automatic aeration control system on the basis of the actual respiration of the cells. The simultaneous use of the automatic aeration apparatus and a turbomixer of great shear stress revealed that some effects of agitation are independent of aeration. These effects of agitation are manifested in two ways: (1) in the increased break down of the cell clumps, thus assuring large free cell surfaces for contact with the substrates; and (2) in the increased mixing effect, which assures a continuous mass transfer towardes the free cell surfaces. These effects of the agitation can improve the yield when the O2 level is maintained near to the saturation value. By means of an automatic aeration control system, the influence of carbon dioxide on the metabolism of hyphae and the production of penicillin was found to be demonstrably inhibitory when the dissolved oxygen was above the critical concentration in the culture liquid. This result is supporting evidence for the assumption that aeration is necessary to biosynthetic processes in two equally important ways: (1) to maintain the oxygen level above the critical value; and (2) to assure ventilation, by which the carbon dioxide level may be kept below its inhibitory critical value.
An 8‐liter continuous flow culture apparatus for laboratory production of microorganisms
Authors: Tempest D. W.
Published: December 2004

The construction of a “Porton type” chemostat of 8‐l. working volume, based on the New Brunswick Scientific Co., Inc., Model F‐14 Fermentor, is detailed. Instrumentation for temperature, pH, and foam control, and for medium supply are described and operational problems discussed.
Studies on the plateau in oxygen uptake during exertion of biochemical oxygen demand by pure cultures of bacteria
Authors: Bhatla M. N. , Gaudy A. F.
Published: December 2004

Evidence for generation of the plateau in oxygen uptake during exertion of carbonaceous BOD by pure cultures was sought by making long term Warburg studies using glucose and phthalic acid as substrates. One organism, tentatively identified as Escherichia intermedia, of the 57 tested, exhibited a plateau. Detailed studies on this organism indicated that generation of the plateau depended upon the type of substrate and to some extent upon the initial cell concentration employed, but not upon substrate concentration. Oxygen utilization during the second stage was accompanied by metabolism of secondary extracellular carbon source(s) produced by the cells during metabolism of the original extracellular carbon source (glucose) in the first phase of O2 uptake. The secondary substrate was registered as volatile acids. Selective inhibition of protein synthesis at various times during oxygen uptake led to the conclusion that the plateau occurred because of the need for an induction period before the secondary substrate could be metabolized. Using this organism, it was also found that a plateau could be generated during endogenous respiration. This secondary O2 utilization was accompained by uptake of organic materials excreted into the medium by the cells during metabolism of endogenous carbon sources.
Proteases of the genus Bacillus. I. Neutral proteases
Authors: Keay Leonard , Wildi Bernard S.
Published: December 2004

B. subtilis NRRL B3411 neutral protease has been extensively purified by solvent, and salt fractional ion, pigment removal with DEAE‐cellulose followed by chromatography on hydroxylapatite, and a final passage through a Sephadex G‐100 column. The neutral protease was shown to be homogeneous by disc gel and cellulose acetate electrophoresis, gel filtration chromatography, and ultra‐centrifugation. The molecular weight was determined by osmometry and ultracentrifugation to be about 38–42,000 and the amino acid composition and zinc content determined. The general properties of the enzyme, pH‐activity relationship, stability, effect of inhibitors, and specificity are discussed. Comparative studies were carried out on the B. subtilis NRRL B3411 and B. subtilis var. amylosacchariticus neutral proteases and these enzymes were found to be indistinguishable by the methods used, but quite distinct from the thermostable enzyme thermolysin from B. thermoprotcolyticus.
Pilot plant isolation of transaldolase from Candida utilis
Authors: Blair H. E. , Charm S. E. , Wallace D. , Matteo C. C. , Tsolas O.
Published: December 2004

Through the use of pilot plant equipment, transaldolase types I, II, and III (from Candida utilis) have been separated and purified. The procedure includes a time sensitive solvent fractionation below 0°C, ion exchange chromatography, and crystalization. The enzyme yield represents a 41% recovery of crystalline type III and partially purified types I and II.
Significance of microbial interactions in control of microbial ecosystems
Authors: Gall Lorraine S.
Published: December 2004

A microbial ecosystem represents a delicately balanced population of microorganisms each interacting with and influencing the other members of the population. An understanding of the nature and effects of these interactions is essential to improving the performance of these ecologies, which are important, in such diverse processes as biological waste treatment procedures, water pollution abatement, industrial fermentations, human or animal digestives processes and in soil. There are several types of mocrobial interactions, such as commensalism, inhibition, food competition, predation, parasitism, and synergism, which either singly or in combination may influence the functioning of the microbial ecology.

To understand interactions, it is necessary to perform a detailed study of the physiology of the individual predominating microorganisms to establish their requirements with respect to such environmental factors as nutrients, temperature, pH, oxidation‐reduction potential, removal of waste products, or toxic materials which may be involved in control processes and to determine how these factors affect their capabilities. The sum total of this information will indicate the possible interactions between the microorganisms and will form the basis for conducting experiments either in the laboratory or with mathematical models. Such experiments will lead to an understanding of microbial activities and to the formulation of control measures, often using an alteration of the environmental factors for regulation of the microbial ecologies. Extensive research remains to be done on the microbial interact inns in obtain the desired, precise control of these ecological processes.
Capsular protection against virulent coliphage infection
Authors: Paynter M. J. B. , Bungay H. R.
Published: December 2004

The ecological significance of bacterial capsules when virulent bacteriophages are present was explored by exposing continuous cultures of Escherichia coli ATCC 11303, in various stages of capsulation and clumping, to a virulent coliphage, T2. Only partial protection was provided by capsulation, but this could be a factor affecting survival in complex mixed cultures.
Responses in continuous cultures of lysogenic Escherichia coli following induction
Authors: Paynter M. J. B. , Bungay H. K.
Published: December 2004

Bacteriophages are widely distributed in nature and may be important factors in regulating populations of their hosts. Model continuous culture systems of a single bacterial species and a temperate parasitic phage have been studied. Steady state cultures of lysogenic Escherichia coli 159T− (λcts) produced a small quantity of free λ cts phage. Temperature shocking such a culture resulted in a sharp increase in phage concentration with a concomitant fall in cell population. With time the system returned to a steady state condition.
An analysis of models describing predator‐prey interaction
Authors: Canale Raymond P.
Published: December 2004

Mathematical models of the interaction between predator and host populations have been expressed as systems of nonlinear ordinary differential equations. Solutions of such systems may be periodic or aperiodic. Periodic, oscillatory solutions may depend on the initial conditions of the system or may be limit cycles. Aperiodic solutions can, but do not necessarily, exhibit oscillatory behavior. Therefore, it is important to characterize predatory‐prey models on the basis of the possible types of solutions they may possess. This characterization can be accomplished using some well‐known methods of nonlinear analysis. Examination of the system singular points and inspection of phase plane portraits have proved to be useful techniques for evaluating the effect of various modifications of early predator‐prey models. Of particular interest is the existence of limit cycle oscillations in a model in which predator growth rate is a function of the concentration of prey.
Oxidation‐reduction potential and concomitant growth patterns of cultures of Earle's “L” cells in centrifuge bottle spinners
Authors: Daniels W. F. , Garcia L. H. , Rosensteel J. F.
Published: December 2004

Previous studies of oxidation‐reduction potential (ORP) variation in monolayer (Roux bottle) cultures pointed out the need for data on pH and ORP patterns in simple spinner cultures. This information was desirable for optimizing conditions of growth in small 1‐L and New Brunswick fermentors. Results of experiments in 250‐ml centrifuge spinner vessels are presented showing that incubation of media prior to inoculation induces desirable qualities reflected in better growth. The importance of initial ORP values of the medium is discussed. The relationship of ORP levels to yield and longevity of cell growth is also considered. The ORP level of the medium at inoculation is shown to be effected by previous incubation.
A continuous, multistage tower fermentor. II. Analysis of reactor performance
Authors: Falch Edvard A. , Gaden Elmer L.
Published: December 2004

A method for analyzing the reactor behavior of a continuous, multistage tower fermentor is described. A model consisting of a system of interconnected, ideal subreactors is set up on the basis of the fermentor's configuration and flow pattern. The residence time distribution curve is used to test the validity of the model and the relative quantities of flow streams and regions in the model are determined. A least‐square fitting procedure between measured and calculated distribution curves is used to identify the proper model. The application of this method to real cultivation conditions is also discussed. Using this approach, the multistage tower fermentor is shown to be equivalent to a cascade of four perfectly mixed tanks with a backtracking stream between stages. The extent of backflow under various conditions has also been determined.
Studies on the kinetics and mechanism of BOD exertion in dilute systems
Authors: Jennelle E. M. , Gaudy A. F.
Published: December 2004

The mechanisms and kinetic course of BOD exertion were compared in both open and closed systems. Two open reactors, a simulated stream device, and an open stirred reactor were employed, and the closed systems consisted of standard BOD bottles and 2.4‐liter vessels. In the closed systems, both quiescent and stirred conditions of incubation were examined. Biological solids concentration, bacteria and protozoa concentration, substrate analysis, and chemical oxygen demand as well as biochemical oxygen utilization were employed to assess the performance of these systems.

Oxygen uptake rate constants were observed to increase with increasing concentration o carbon source, thus militating against irect use of the usual dilution technique for predicting rate of deoxygenation in receiving streams. The relationship between specific O2 uptake rate and substrate concentration approximated a hyperbolic function similar to the Mono relationship for specific growth rate and substrate concentration. A technique using an open stirred reactor than the standard BOD bottle dilution technique is recommended.
The effect of small amounts of sodium hypochlorite on the growth of Earl's “L” cells in suspension growth
Authors: Jordan William C. , Rosensteel John F. , Daniels William F. , Garcia Luis H.
Published: December 2004

Of several candidate disinfectants for use in tissue culture work, especially suspension cultures, sodium hypochlorite solution was selected to test its effect on growing cells. Metabolizing cells reduce, sodium hypochlorite oxidizes ; therefore NaOCl leakage into such systems must be neutralized with no untoward effects on the cells.

Dilutions of routine disinfectant‐grade sodium hypochlorite were tested against cell cultures. Those exposed to 15.62 to 31.25 ppm of NaOCl grew with no
apparent cell damage.
Optimal conditions for gramicidin S production in continuous culture
Authors: Blanch H. W. , Rogers P. L.
Published: December 2004

In the present study optimal policies have been evaluated for the production of gramicidin S in multistage continuous culture. An economic objective function was developed which took account of the number and size of the reaction vessels, the costs involved in antibiotic extraction, substrate costs, and variability in the selling price of gramicidin S. Optimal values of temperature and pH were 28.3 and 7.24, respectively, and independent of the stage in the system. Using the discrete maximum principle it was shown that a “cut‐off” point existed for the selling price of the antibiotic below which production was no longer profitable. Furthermore it was established that beyond 3 stages in a multistage system, only marginal gains in profitability could be made (viz., an increase in 6.3% on going from a 3‐stage to a 4‐stage system).
A mechanism of microbial cell growth
Authors: Verhoff F. H. , Sundaresan K. R. , Tenney M. W.
Published: December 2004

Presently empirical expressions, especially the Monod equation, are used to quantitatively relate microbial growth rate to limiting substrate concentration in the solution. In this paper microbial growth is postulated to occur by a mechanism involving a mass transfer or assimilation process. The assimilation process is assumed to be substrate mass transfer limited and hence proportional to the limiting substrate concentration. The ingestion is assumed independent of limiting substrate concentration and only dependent upon internal reaction rates. The quantitative relationship between limiting substrate and microbial growth rate resulting from this mechanism is developed. Under certain limiting conditions this expression is shown to reduce to the Monod equation and under other conditions it reduces to the Lotka‐Volterra relationship. This mechanism is applied to batch and continuous cultures and the results obtained are compared quantitatively with experiment.
Measurement of yeast concentrations in liquid hydrocarbon fermentations: Influence of experimental conditions and statistical significance of the results obtained
Authors: Concone Bruno R. V. , Hiss Haroldo , Pilar Maria Del , Paz G. , Patricio Carolina G. , Borzani Walter
Published: December 2004

The influence of the following factors on the measurement of yeast concentration in liquid hydrocarbon fermentations was studied: surfactant, type (Tween 20, Tween 80, and G 3300), yeast concentration (0.215 to 0.272 and 3.37 to 4.08 g/liter, as dry matter), oil concentration (8.32 and 61.6 g/liter), surfactant, concentration (0.515, 1.030, 1.545, and 2.060 g/liter), and time of contact of the surfactant with the oil‐yeast‐aqueous medium mixture (2 and 10 min). The statistical significance of the obtained results was determined.