Showing papers by "University of Marburg published in 1991"

GLI3 zinc-finger gene interrupted by translocations in Greig syndrome families

Abstract: The Greig cephalopolysyndactyly syndrome (GCPS) is an autosomal dominant disorder affecting limb and craniofacial development in humans. GCPS-affected individuals are characterized by postaxial polysyndactyly of hands, preaxial polysyndactyly of feet, macroephaly, a broad base of the nose with mild hypertelorism and a prominent forehead. The genetic locus has been pinpointed to chromosome 7p13 by three balanced translocations associated with GCPS in different families. This assignment is corroborated by the detection of two sporadic GCPS cases carrying overlapping deletions in 7p13 (ref. 7), as well as by tight linkage of GCPS to the epidermal growth factor receptor gene in 7p12-13 (ref. 8). Of the genes that map to this region, those encoding T cell receptor-gamma, interferon-beta 2, epidermal growth factor receptor, and Hox1.4, a potential candidate gene for GCPS, have been excluded from the region in which the deletions overlap. Here we show that two of the three translocations interup the GLI3 gene, a zinc-finger gene of the GLI-Kruppel family already localized to 7p13 (refs 5, 6). The breakpoints are within the first third of the coding sequence. In the third translocation, chromosome 7 is broken at about 10 kilobases downstream of the 3' end of GLI3. Our results indicate that mutations disturbing normal GLI3 expression may have a causative role in GCPS.

Transcriptional control by nuclear receptors.

Abstract: Gene regulation by steroid hormones is accomplished by a variety of different mechanisms leading to induction or repression of particular genes. These mechanisms are all mediated by a single class of intracellular hormone receptors, which in the unliganded state are maintained in an inactive form by association with other cellular proteins, including hsp90. Induction of the mouse mammary tumor virus (MMTV) requires binding of the hormone receptor to a hormone-responsive element (HRE) that is precisely organized in a phased nucleosome. After receptor binding, changes in chromatin structure are detected that correlate with binding of transcription factors, including nuclear factor I, to the MMTV promoter. However, although nuclear factor I acts as a basal transcription factor on the MMTV promoter it does not cooperate with the hormone receptors in terms of binding to free DNA, and mutation of the nuclear factor I binding site does not eliminate hormonal stimulation. This residual induction is mediated by oc...

The S protein of bovine coronavirus is a hemagglutinin recognizing 9-O-acetylated sialic acid as a receptor determinant.

Abstract: The S protein of bovine coronavirus (BCV) has been isolated from the viral membrane and purified by gradient centrifugation. Purified S protein was identified as a viral hemagglutinin. Inactivation of the cellular receptors by sialate 9-O-acetylesterase and generation of receptors by sialylation of erythrocytes with N-acetyl-9-O-acetylneuraminic acid (Neu5,9Ac2) indicate that S protein recognizes 9-O-acetylated sialic acid as a receptor determinant as has been shown previously for intact virions. The second glycoprotein of BCV, HE, which has been thought previously to be responsible for the hemagglutinating activity of BCV, is a less efficient hemagglutinin; it agglutinates mouse and rat erythrocytes, but in contrast to S protein, it is unable to agglutinate chicken erythrocytes, which contain a lower level of Neu5,9Ac2 on their surface. S protein is proposed to be responsible for the primary attachment of virus to cell surface. S protein is proposed to be responsible for the primary attachement of virus to cell surface receptors. The potential of S protein as a probe for the detection of Neu5,9Ac2-containing glycoconjugates is demonstrated.

Hole transport in 1,1‐bis(di‐4‐tolylaminophenyl)cyclohexane

Abstract: Hole mobilities have been measured in vapor deposited films of 1,1‐bis(di‐4‐tolylaminophenyl)cyclohexane over an extended range of fields and temperatures. At 295 K, the mobility is approximately 10−2 cm2/V s, the highest value for a disordered molecular solid reported thus far. Monte Carlo simulations of random walk in a geometrically and energetically disordered medium demonstrate that the time dependence of the photocurrent and the field and temperature dependencies of the mobility can be described quantitatively in terms of the inherent disorder and its effect on charge transport. No polaronic or trapping phenomena need to be invoked to reproduce even subtle features of the experimental results.

Subtotal parathyroidectomy versus total parathyroidectomy and autotransplantation in secondary hyperparathyroidism: a randomized trial.

Abstract: In a randomized study subtotal parathyroidectomy (sPTX) was compared with total parathyroidectomy and autotransplantation of fresh tissue (PTX+AT) in 40 patients with severe secondary hyperparathyroidism (HPT). After surgery both groups were followed at 19±6 months (PTX +AT) and 19±7 months (sPTX) and at 43±9 months (PTX+AT) and 40±7 months (sPTX). There were 17 patients alive in each group at the time of the second follow-up. After sPTX, 2 patients required re-operation because of recurrent disease originating from the remaining parathyroid gland in the neck and another 2 patients were hypercalcemic at follow-up. After PTX + AT both serum calcium and alkaline phosphatase normalized significantly more often (p <0.03) than after sPTX. Re-operations were not required in this group. Radiological signs also improved significantly more after PTX+AT, as did clinical signs like pruritus (p< 0.005) and muscle weakness (p<0.04). These results and the fact that in recurrent disease a re-operation at the autograft in the forearm is simpler than a re-operation in the neck, lead to the recommendation that PTX+ AT should be considered as the method of choice in the surgical treatment of secondary HPT.

Evidence for the Altruistic Personality from Data on Accident Research

Abstract: The aim of this study was to test whether the concept of an altruistic personality was valid for first aiders who intervened to help the victims of a traffic accident. We derived a number of relevant personality variables that should be related to the willingness to administer first aid. These include locus of control, social responsibility, belief in a just world, empathy, and instrumentality. We obtained data from proven first aiders who had intervened after a traffic accident. Thirty-four of these first aiders were matched to respondents from a subject pool on the basis of sex, age, and socioeconomic status. In addition, the willingness of these respondents to offer help after a traffic accident was taken into account. Only people who indicated that they had witnessed an accident and had not helped were included in the control group. Multivariate analyses of variance and covariance indicated that proven first aiders deviated from the control group on several dimensions: They described themselves as more internal, believed more in a just world, and emphasized more social responsibility and empathy.

dc and transient photoconductivity of poly(2-phenyl-1,4-phenylenevinylene).

Abstract: Generation and transport of charge carriers in poly(2-phenyl-1,4-phenylenevinylene) has been investigated by means of dc and transient photoconductivity. Photocarrier production is temperature and field assisted and is appropriately described within the framework of the one-dimensional Onsager theory of geminate-pair dissociation. The geminate pairs are formed by disorder-assisted dissociation of primarily excited localized singlet excitations of chain segments. At high fields the geminate-pair yield is of order unity. Time-of-flight signals are characteristic of a disordered solid. After an initial dispersive decay, a plateau is attained, followed by a long-lasting tail. Hole mobilities decrease with increasing electric field---suggestive of the importance of off-diagonal disorder---and carry a temperature dependence characteristic of hopping within a Gaussian density of states 90 meV in width. No evidence for polaronic effects is found.

Blood pressure and sleep apnea: results of long-term nasal continuous positive airway pressure therapy.

Abstract: Arterial blood pressure patterns in 12 men with sleep apnea and arterial hypertension were studied at baseline and after 6 months’ therapy with nasal continuous positive airway pressure (nCPAP). Preex

Alternative splicing of fosB transcripts results in differentially expressed mRNAs encoding functionally antagonistic proteins.

Abstract: We show that serum-stimulated fibroblasts transiently express two different forms of fosB mRNA, which are generated by alternative splicing of the transcript from a single gene. In addition to the known long form (fosB-L), encoding a protein of 338 amino acids (FosB-L), a second shorter form (fosB-S) with a deletion of 140 bp was detected. This deletion creates a stop codon 3' to the leucine repeat, giving rise to a protein of 237 amino acids (FosB-S) lacking the carboxyl terminus of FosB-L. Only the long FosB form efficiently induces transformation in mouse and rat fibroblast cell lines and trans-represses the c-fos promoter. Both of these functions are suppressed by coexpressed FosB-S. Upon serum stimulation, maximum expression of the oncogenic fosB-L form precedes the expression of the antagonistic fosB-S form, indicating a new mechanisms regulating the action of members of the Fos family. However, FosB-L and FosB-S do not differ in all trans-regulatory properties: Trans-activation of a 5x TRE-CAT reporter construct in HeLa and NIH-3T3 cells was found with both FosB forms. These observations suggest a correlation between fosB-induced transformation and trans-repression, thus pointing to different mechanisms involved in transformation by fosB and c-fos/v-fos.

Analysis of prognostic factors in 766 patients with small cell lung cancer (SCLC): the role of sex as a predictor for survival.

Abstract: The data of 766 patients participating in three German multicentre trials were analysed with regard to the relationship between baseline characteristics and prognosis in small cell lung cancer (SCLC). The central aim of this analysis has been to evaluate the role of gender as an independent prognostic factor in SCLC. The minimum follow-up period for the 652 male and 114 female patients was 36 months. Female patients were shown to have a higher complete remission rate (35% vs 25%), a superior median survival (ms) (12.1 months (mo) vs 9.8 mo), and a favourable 2-year survival rate (2ys) (19% vs 8%) to male ones. Various other prognostic factors have been proved to be significant, such as extent of disease, clinical performance status, and history of smoking, whereas weight loss prior to chemotherapy and age have been less important factors. We have been able to ascertain that women's responses were better than those of male patients independent of any other relevant prognostic variable. Furthermore, results were found to be even more advantageous for female patients with additional favourable prognostic parameters, i.e. for patients with limited disease (ms 15.2 mo vs 12.0 mo; 2ys 29% vs 9%) or with good performance status (ms 13.4 mo vs 10.4 mo; 2ys 24% vs 7%). A most remarkable observation was made in that the favourable prognostic effect of the female gender was restricted to patients aged less than 60 years (ms 13.3 mo vs 10.1 mo; 2ys 26% vs 5%), whereas for older women no advantages over men's results were established (ms 9.3 ml vs 9.1 mo; 2ys 8% vs 7%). A proportion of 32% of female patients with limited disease aged less than 60 years achieved a 3-year survival rate. We conclude (a) that sex constitutes a major prognostic factor in SCLC and is especially useful as a predictor for long-term survival, and (b) that the favourable prognostic value of the female sex is restricted to younger patients.

Site-specific mutagenesis identifies three cysteine residues in the cytoplasmic tail as acylation sites of influenza virus hemagglutinin.

Abstract: The hemagglutinin (HA) of influenza virus is a type I transmembrane glycoprotein which is acylated with long-chain fatty acids. In this study we have used oligonucleotide-directed mutagenesis of cloned cDNA and a simian virus 40 expression system to determine the fatty acid binding site in HA and to examine possible functions of covalently linked fatty acids. The results show that the HA is acylated through thioester linkages at three highly conserved cysteine residues located in the cytoplasmic domain and at the carboxy-terminal end of the transmembrane region, whereas a cysteine located in the middle of the membrane-spanning domain is not acylated. Mutants lacking fatty acids at individual or all three attachment sites acquire endoglycosidase H-resistant oligosaccharide side chains, are cleaved into HA1 and HA2 subunits, and are transported to the plasma membrane at rates similar to that of wild-type HA. All mutants are membrane bound and not secreted into the medium. These results exclude transport signal and membrane-anchoring functions of covalently linked fatty acids for this integral membrane glycoprotein. Furthermore, lack of acylation has no obvious influence on the biological activities of HA: cells expressing fatty acid-free HA bind to and, after brief exposure to mildly acidic pH, fuse with erythrocytes; the HA-induced polykaryon formation is not impaired, either. Other possible functions of covalently linked fatty acids in integral membrane glycoproteins which cannot be examined in conventional cDNA expression systems are discussed.

Reductive formation of carbon monoxide from CCl4 and FREONs 11, 12, and 13 catalyzed by corrinoids.

Abstract: In an earlier publication, we reported that corrinoids catalyze the sequential reduction of CCl4 to CHCl3, CH2Cl2, CH3Cl, and CH4 with titanium(III) citrate as electron donor [Krone, U. E., Thauer, R. K., & Hogenkamp, H. P. C. (1989) Biochemistry 28, 4908-4914]. However, the recovery of these products was less than 50%, indicating that other products were formed. We now report that, under the same experimental conditions, CCl4 is also converted to carbon monoxide. These studies were extended to include FREONs 11, 12, 13, and 14. Corrinoids were found to catalyze the reduction of CFCl3, CF2Cl2, and CF3Cl to CO and, in the case of CFCl3, to a lesser extent, to formate. CF4 was not reduced. The rate of CO and formate formation paralleled that of fluoride release. Both rates decreased in the series CFCl3, CF2Cl2, CCl4, and CF3Cl. The reduction of CFCl3 gave, in addition to CO and formate, CHFCl2, CH2FCl, CH3F, C2F2Cl2, and C2F2Cl4. The product pattern indicates that the corrinoid-mediated reduction of halogenated C1-hydrocarbons involves the intermediacy of dihalocarbenes, which may be a reason why these compounds are highly toxic for anaerobic bacteria.

Daily torpor in the Djungarian hamster (Phodopus sungorus): interactions with food intake, activity, and social behaviour

Abstract: In Djungarian hamsters,Phodopus sungorus, daily torpor occurs spontaneously in winter in the presence of abundant food, but individuals show different tendencies to enter torpor. The results show that in hamsters fed rodent chow ad libitum individual torpor frequencies were negatively correlated with both food consumption and the amount of nocturnal locomotor activity. Provision of cafeteria diet at ambient temperatures below thermoneutrality significantly lowered torpor frequencies and induced body weight gains. However, in hamsters fed seeds with a high fat or carbohydrate content (i.e., sunflower seeds or wheat, respectively) neither a decrease of torpor frequencies nor an increase of body weights was observed. The results suggest that in Djungarian hamsters, daily torpor is an intrinsic component of energy balance control and is functionally linked to individual physiological adjustments of food consumption and foraging activity. In addition, the employment of daily torpor can be affected by social interactions, since the long-term pattern of alternations between torpor and normothermia was found to be synchronized in breeding pairs caged together.

Induction of stilbene synthase by Botrytis cinerea in cultured grapevine cells

Abstract: The interaction between Botrytis cinerea Pers. and grapevine (Vitis vinifera L.) was studied in a model system of reduced complexity. Cultured plant cells and fragments of fungal cell wall were used to simulate some of the processes taking place upon infection of grapevine with B. cinerea. A soluble glucan elicitor was prepared from the fungal cell wall by acid hydrolysis. Like the insoluble wall preparation, the soluble fragment derived from the cell wall acted upon plant cells in eliciting stilbene formation. In grapevine cells, the interaction with the fungus led to a dramatic shut-off general protein synthesis and to the selective formation of a small set of proteins involved in induced resistance. The proteins synthesized de novo with highest rates were stilbene synthase (StiSy) and l-phenylalanine ammonia-lyase (PAL). Stilbene synthase was purified to apparent homogeneity and its molecular properties were characterized. The enzyme is a homodimer with subunit Mr 43 000 and pl = 5.4. Although there were indications of the presence of isoenzymes, these were not distinguished by charge differences. In size, the grapevine StiSy shows microheterogeneity and differs from the appreciably larger enzyme prepared from peanut. Prior to induction by fungal attack, virtually no stilbenes are formed in the plant cell. Upon induction of the pathway leading to the stilbene resveratrol, StiSy activity determines the ratelimiting step in the metabolic sequence. The highly induced grapevine cells produce and secrete resveratrol and derivatives which are known to be fungistatic.

Liver fibrosis: perspectives in pathobiochemical research and clinical outlook.

Abstract: Disturbances of the equilibrium between parenchyma and extracellular matrix, leading to a disproportionate increase in and an irregular deposition of newly formed connective tissue components (fibrosis), is a common sequel of chronic active liver diseases with serious clinical consequences. Significant progress has been made in recent years in the analysis of the structural composition of extracellular matrix in normal and fibrotic liver and in the dissection of the molecular and cellular mechanisms of exaggerated extracellular matrix deposition in necroinflammatory areas. Under the influence of inflammatory stimuli, perisinusoidal, retinoid-storing cells (Ito cells, parasinusoidal lipocytes), which are qualitatively and quantitatively the most important connective tissue-producing cell type in human and animal liver, transform to myofibroblast-like cells. Activation and transformation of perisinusoidal cells are mediated by paracrine and autocrine loops involving transforming growth factor beta as the main fibrogenic mediator, which is secreted by activated liver macrophages, possibly also by endothelial cells, and liberated by disintegrated thrombocytes. The molecular and cellular interactions during liver fibrogenesis have become a model for a number of other organ fibrotic processes, wound repair and even atherogenesis. Therapeutic interference with the early steps of fibrogenesis seems feasible but a breakthrough has not yet been achieved. For clinical-chemical, non-invasive diagnosis and monitoring of ongoing fibrogenesis, a rather limited repertoire of more or less organ- and disease-unspecific parameters is available. Split products of the extracellular maturation pathway of the procollagen types, laminin and hyaluronan, can be assayed but the clinical interpretation of the results has to be made with caution. Strategies and major topics of future pathobiochemical and clinically oriented research are highlightened.

How "blind" are double-blind studies?

Abstract: Psychopharmacological studies usually attempt to eliminate "nonspecific" influences on outcome by double-blind designs. In a randomized, double-blind comparison of alprazolam, imipramine, and placebo, the great majority of panic disorder patients (N = 59) and their physicians were able to rate accurately whether active drug or placebo had been given. Moreover, physicians could distinguish between the two types of active drugs. Inasmuch as correct rating was possible halfway through treatment, concerns about the internal validity of the double-blind strategy arise.

Chemotaxis and nod Gene Activity of Bradyrhizobium japonicum in Response to Hydroxycinnamic Acids and Isoflavonoids.

Abstract: For Bradyrhizobium japonicum, the chemotactic and the nod gene-inducing effects of hydroxycinnamic acids and two of their derivatives were compared with those of isoflavonoids. Only the hydroxycinnamic acids were strong chemoattractants, while the other substances tested were chemotactically inactive. Besides the known nod gene induction by isoflavonoids, a weak nod gene induction by coniferyl alcohol, chlorogenic acid, and ferulic acid was found.

Basic FGF-like immunoreactivity in the developing and adult rat brainstem

Abstract: Although a variety of in vitro and in vivo actions of basic fibroblast growth factor (bFGF) on neuronal cells have been documented, the physiological role of this protein in the nervous system is still contested. Since the distribution of a molecule in the nervous system may provide cues for an understanding of its possible roles, we have begun to study its cellular localization in the central and peripheral nervous system using immunocytochemistry with an anti-bFGF-specific antibody. Here we provide an account on the distribution of bFGF-like immunoreactivity (bFGF-IR) in the brainstem of the developing and adult rat. Basic FGF-IR was found to be widely distributed in motor and sensory nuclei. In all nuclei examined, only subpopulations of neurons were stained. Different staining patterns were found. For example, in the red nucleus weakly or unstained perikarya were surrounded by numerous immunoreactive fibers, often in close contact with the neuronal surface. In the reticular formation and facial nerve, many neuronal cell bodies showed a strong IR that extended into the processes. Glial cells were consistently unstained. During early postnatal development changes of the distribution of bFGF IR were found. From this wide distribution pattern of bFGF-IR, we conclude that bFGF may have more general and, possibly, diverse functions rather than a restricted role for a particular subset of neurons. Variations in the staining pattern of nerve cell bodies in a single nucleus may suggest a function related to neuronal activity.

Glucagon-like peptide-1(7-36) amide is a new incretin/enterogastrone candidate.

Abstract: Cloning and sequence analysis of cDNAs and DNA fragments from genomic libraries has led to a dramatic increase in understanding of the glucagon-related peptides in recent years. The primary structure of the biosynthetic precursor of glucagon (preproglucagon) has been elucidated. The complex structural connec- tions between the multiple molecular forms of the glucagon-like peptides in tissues and in the circulation have been determined [ 1,2]. Mammalian proglucagon consists of 160 amino acid residues and is synthesized in the islets of Langerhans, intestine and brain. An exciting recent finding is that in addition to glucagon the preproglucagon gene in mammals encodes two additional peptides with struc- tural similarity to glucagon, termed glucagon-like peptide-1 and -2 (GLP-I and GLP-2). The truncated form of GLP-1, GLP-1(7-36) amide, which is secreted by the mammalian intestine, strongly stimulates insu- lin secretion and inhibits gastric acid secretion. This review focuses mainly on the truncated form of GLP-1. since a rapidly increasing number of reports indicate a remarkable interest of investigators in this particular hormone, which actually fulfills the classical role of an ‘enterogastrone’ and ‘incretin’ hormone. The purpose here is to describe what is known so far about the origin, processing, organ distribution and actions of this peptide and to search for promising future direc- tions of further investigations.

Anomalous time-independent diffusion of charge carriers in a random potential under a bias field

Abstract: We present Monte Carlo simulation results for time-independent drift and spatial spreading of a packet of charge carriers executing a random walk within a manifold of hopping sites under a bias field. The shape of the density-of-states profile is assumed to be Gaussian (width [sgrave]). The ratio eD/μkT, eaual to unity for ordinary diffusion, is found to increase dramatically with increasing disorder and bias field. For [sgrave]/kT=3.5 and fields of order 106Vcm−1, eD/μk T reaches values of order 103. The effect accounts for the anomalous spreading of time-of-flight profiles often seen in photocarrier transit time studies on various polymeric systems. The role of disorder in charge-carrier transport is emphasized.

Influenza A virus infection of macrophages. Enhanced tumor necrosis factor-alpha (TNF-alpha) gene expression and lipopolysaccharide-triggered TNF-alpha release.

Abstract: We have previously shown that infection of macrophages by influenza A virus is capable of priming for a high TNF-alpha production in response to LPS. The present study was designed to examine in more detail TNF-alpha gene expression and TNF-alpha protein release of virus-infected, murine PU5-1.8 macrophages in the presence or absence of low and by itself rather inefficient concentrations of LPS (10 ng/ml). Although influenza A virus infection alone induced a massive TNF-alpha mRNA accumulation, translation into the bioactive TNF-alpha protein was low as intra- and extracellularly determined by bioassay, specific ELISA and Western blot. However, when LPS was added simultaneously or up to 4 h after infection, a high TNF-alpha production was initiated. The virus-induced TNF-alpha mRNA accumulation appeared to be due to both transcriptional and post-transcriptional changes: an enhanced TNF-alpha gene transcription as determined by nuclear run-on transcription assay and a markedly prolonged half-life of TNF-alpha mRNA as shown in actinomycin D-treated macrophages. These findings imply that influenza A virus may 1) either directly or indirectly stimulate TNF-alpha gene transcription activators or may interfere with labile transcription repressor proteins and 2) may stabilize TNF-alpha mRNA by delaying its degradation. Both mechanisms, taken together, prime influenza A virus-infected macrophages for a high TNF-alpha release in response to LPS which, as clinical cases show, may adversely affect patients with combined influenza A virus and bacterial infections.

Isoflavonoid-inducible resistance to the phytoalexin glyceollin in soybean rhizobia.

Abstract: The antibacterial effect of the soybean phytoalexin glyceollin was assayed using a liquid microculture technique. Log-phase cells of Bradyrhizobium japonicum and Sinorhizobium fredii were sensitive to glyceollin. As revealed by growth rates and survival tests, these species were able to tolerate glyceollin after adaptation. Incubation in low concentrations of the isoflavones genistein and daidzein induced resistance to potentially bactericidal concentrations of glyceollin. This inducible resistance is not due to degradation or detoxification of the phytoalexin. The inducible resistance could be detected in B. japonicum 110spc4 and 61A101, representing the two taxonomically divergent groups of this species, as well as in S. fredii HH103, suggesting that this trait is a feature of all soybean-nodulating rhizobia. Glyceollin resistance was also inducible in a nodD1D2YABC deletion mutant of B. japonicum 110spc4, suggesting that there exists another recognition site for flavonoids besides the nodD genes identified so far. Exudate preparations from roots infected with Phytophthora megasperma f. sp. glycinea exhibited a strong bactericidal effect toward glyceollin-sensitive cells of B. japonicum. This killing effect was not solely due to glyceollin since purified glyceollin at concentrations similar to those present in exudate preparations had a much lower toxicity. However, glyceollin-resistant cells were also more resistant to exudate preparations than glyceollin-sensitive cells. Isoflavonoid-inducible resistance must therefore be ascribed an important role for survival of rhizobia in the rhizosphere of soybean roots.

Common features in the transport behaviour of diverse glassy solids: Exploring the role of disorder

Abstract: Key results of time-of-flight drift mobility measurements on silicon and germanium backbone polymers are reviewed. Transport in these polymers displays a convoluted and yet familiar pattern of electric field and temperature dependences similar in remarkable detail to behaviour already reported for a very diverse collection of disordered molecular solids. The latter, while varied in composition and morphology, all share at least two common features, namely firstly transport controlled by interaction with localized states which are either hopping sites or shallow traps in communication with a band and secondly disorder. We explore in this paper the application of what is arguably the simplest model (derived from Monte Carlo simulation) of transport incorporating these characteristics. Consideration will be restricted to hopping among a spatially regular array of sites made energetically inequivalent by disorder. Thus, neither positional disorder nor site relaxation is explicitly considered. Some re...

Purification and properties of 4-hydroxybutyrate coenzyme A transferase from Clostridium aminobutyricum.

Abstract: A new coenzyme A (CoA)-transferase from the anaerobe Clostridium aminobutyricum catalyzing the formation of 4-hydroxybutyryl-CoA from 4-hydroxybutyrate and acetyl-CoA is described The enzyme was purified to homogeneity by standard techniques, including fast protein liquid chromatography under aerobic conditions Its molecular mass was determined to be 110 kDa, and that of the only subunit was determined to be 54 kDa, indicating a homodimeric structure Besides acetate and acetyl-CoA, the following substrates were detected (in order of decreasing kcat/Km): 4-hydroxybutyryl-CoA, butyryl-CoA and propionyl-CoA, vinyl-acetyl-CoA (3-butenoyl-CoA), and 5-hydroxyvaleryl-CoA In an indirect assay the corresponding acids were also found to be substrates; however, DL-lactate, DL-2-hydroxybutyrate, DL-3-hydroxybutyrate, crotonate, and various dicarboxylates were not