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At least 235 records · Page 13Linked to original sources
PubMed1982

Non-opiate beta-endorphin fragments and dopamine--I. The neuroleptic-like gamma-endorphin fragments interfere with the behavioural effects elicited by small doses of apomorphine.

In rats, the beta-endorphin fragment, 6-17 (des-enkephalin-gamma-endorphin, DE gamma E), dose-dependently antagonized the reduction of the rate of locomotion and rearing induced by small doses of apomorphine. Structure-activity studies revealed that the active moiety of gamma-endorphin fragments with respect to counteracting apomorphine-induced behavioural changes resides in the fragment 6-17. The influence of DE gamma E appeared to be specific for dopamine systems mediating apomorphine-induced hypomotility, since DE gamma E hardly affected apomorphine-induced stereotypy and amphetamine-induced behavioural changes. These data suggest that DE gamma E acts as a dopamine antagonist selectively, on those dopamine receptor systems which are stimulated by small doses of apomorphine and which may be located presynaptically. In contrast to acute treatment, administration of DE gamma E for 4 days resulted in an enhancement of apomorphine-induced hypomotility. Thus, the receptor systems involved in these effects of apomorphine may become supersensitive upon (sub)chronic treatment with DE gamma E. The significance of the present findings are discussed in relation to the neuroleptic-like and antipsychotic action of gamma-type endorphins.

Animals↗
PubMed2004

Studies on sulfatides by quadrupole ion-trap mass spectrometry with electrospray ionization: structural characterization and the fragmentation processes that include an unusual internal galactose residue loss and the classical charge-remote fragmentation.

The structural characterization of sulfatides by collisional-activated dissociation (CAD) quadrupole ion-trap tandem mass spectrometric methods with electrospray ionization is described. When subjected to CAD in the negative-ion mode, the [M - H]- ions of sulfatides yield abundant structurally informative ions that permit unequivocal assignments of the long-chain base, and fatty acid constituent including the location of double bond. The identification of the position of the double bond on the fatty acyl substituent is based on the observation of the series of the ions arising from classical charge-remote fragmentation processes similar to those observed by high-energy CAD and by tandem quadrupole mass spectrometry. An unusual internal galactose residue loss due to a rearrangement process was also observed. The [M - H]- ions of sulfatides also dissociates to a ceramide anion, which undergoes consecutive fragmentation processes to yield ions informative for identification of the ceramide moiety and permits distinction the sulfatide with a sphingosine subclass from that with a sphinganine long-chain base subclass. The MS(2)-spectra of the sulfatide subclass with a sphingosine LCB and a alpha-hydroxy fatty acyl substituent (d18:1/hFA-sulfatide) are featured by the prominent ion sets of m/z 568, 550, 540, and 522, originated from a primary cleavage of the fatty acyl CO-CH(OH) bond, and are readily differentiable from those arising from the non-hydroxy sulfatide subclass (d18:1/nFA-sulfatide), in which the ion sets are of low abundance. The fragmentation pathways of sulfatides under low-energy CAD are proposed. The pathways are supported by the MS(2)- and MS(3)-spectra of various compounds, and of their H-D exchanged analogs.

Animals↗
PubMed2005

Fragmentation of negative ions from carbohydrates: part 2. Fragmentation of high-mannose N-linked glycans.

[M + NO3]- And [M + (NO3)2]2- ions were produced by electrospray from neutral high-mannose ([Man](5-9)[GlcNAc]2, [Glc](1-3)[Man](4-9)[GlcNAc]2) N-linked glycans and their 2-aminobenzamide derivatives sprayed from methanol:water containing ammonium nitrate. Low energy collision-induced decomposition (CID) spectra of both types of ions were almost identical and dominated by cross-ring and C-type fragments, unlike the corresponding spectra of the positive ions that contained mainly B- and Y-type glycosidic fragments. This behavior could be rationalized by an initial proton abstraction from various hydroxy groups by the initially-formed anionic adduct. These negative ion spectra were more informative than the corresponding positive ion spectra and contained prominent ions that were diagnostic of structural features such as the composition of individual antennas that were not easily obtainable by other means. C-ions defined the sequence of the constituent monosaccharide residues. Detailed fragmentation mechanisms are proposed to account for many of the diagnostic ions.

Anions↗
PubMed2004

An alternative measure of sleep fragmentation in clinical practice: the sleep fragmentation index.

BACKGROUND AND PURPOSE: Micro-arousals (MA) are commonly considered as sleep components reflecting sleep fragmentation. However, their elucidation is time-consuming, with considerable inter-observer variability. The aim of our study was to investigate the usefulness of a sleep fragmentation index (SFI) to detect sleep disruption in a large sample of patients. PATIENTS AND METHODS: Five-hundred ninety-eight polysomnographic studies made in controls and patients were examined. The SFI was calculated as the total number of awakenings and sleep stage shifts divided by total sleep time. RESULTS: In the whole group a significant correlation was found between the SFI and the MA index (MAI) (P<0.001) with good agreement across a wide range of values. When patients were stratified according to final diagnosis a significant relation was noted for patients with insomnia (P<0.001), parasomnia (P<0.001), circadian schedule disorders (P<0.001) and sleep related breathing disorders (P< 0.001). Lower values were found in controls (P<0.01) and in patients with periodic limb movement disorder and/or restless legs syndrome (P<0.05). In 111 patients having two consecutive recording nights, a good reproducibility was present with no differences between nights (P=ns) and with significant correlation (P<0.001). CONCLUSIONS: The SFI seems to be an accurate, reproducible and easy method to detect sleep fragmentation in patients with sleep disorders. Further studies are needed to validate the usefulness of this tool in clinical practice.

Adult↗
PubMed2006

Determination of Intramolecular delta13C from incomplete pyrolysis fragments. Evaluation of pyrolysis-induced isotopic fractionation in fragments from the lactic acid analogue propylene glycol.

Intramolecular carbon isotope ratios reflect the source of a compound and the reaction conditions prevailing during synthesis and degradation. We report here a method for determination of relative (Deltadelta13C) and absolute (delta13C) intramolecular isotope ratios using the volatile lactic acid analogue propylene glycol as a model compound, measured by on-line gas chromatography-pyrolysis coupled to GC-combustion-isotope ratio mass spectrometry. Pyrolytic fragmentation of about one-third of the analyte mass produces optimal fragments for isotopic analysis, from which relative isotope ratios (Deltadelta13C) are calculated according to guidelines presented previously. Calibration to obtain absolute isotope ratios is achieved by quantifying isotope fractionation during pyrolysis with an average fractionation factor, alpha, and evaluated by considering extremes in isotopic fractionation behavior. The method is demonstrated by calculating ranges of absolute intramolecular isotope ratios in four samples of propylene glycol. Relative and absolute isotope ratios were calculated with average precisions of SD(Deltadelta13C) <0.84 per thousand and SD(delta13C) <3.0 per thousand, respectively. The various fractionation scenarios produce an average delta(13)C range of 2 per thousand for each position in each sample. Relative isotope ratios revealed all four samples originated from unique sources, with samples A, B, and D only distinguishable at the position-specific level. Regardless of pyrolysis fractionation distribution, absolute isotope ratios showed a consistent pattern for all samples, with delta13C(3) > delta13C(2) > delta13C(1). The validity of the method was determined by examining the difference in relative isotope ratios calculated through two independent methods: Deltadelta13C calculated directly using previous methods and Deltadelta13C extracted from absolute isotope ratios. Deviation between the two Deltadelta13C values for all positions averaged 0.1-0.2 per thousand, with the smallest deviation obtained assuming equal fractionation across all fragment positions. This approach applies generally to all compounds analyzed by pyrolytic PSIA.

Calibration↗
PubMed2005

The kinetics of addition and fragmentation in reversible addition fragmentation chain transfer polymerization: An ab initio study.

High-level ab initio calculations of the forward and reverse rate coefficients have been performed for a series of prototypical reversible addition fragmentation chain transfer (RAFT) reactions: R* + S=C(Z)SCH3 --> R-SC*(Z)SCH3, for R = CH3, with Z = CH3, Ph, and CH2Ph; and Z = CH3, with R = (CH3), CH2COOCH3, CH2Ph, and C(CH3)2CN. The addition reactions are fast (ca. 10(6)-10(8) L mol(-1) s(-1)), typically around three orders of magnitude faster than addition to the C=C bonds of alkenes. The fragmentation rate coefficients are much more sensitive to the nature of the substituents and vary from 10(-4) to 10(7) s(-1). In both directions, the qualitative effects of substituents on the rate coefficients largely follow those on the equilibrium constants of the reactions, with fragmentation being favored by bulky and radical-stabilizing R-groups and addition being favored by bulky and radical-stabilizing Z-groups. However, there is evidence for additional polar and hydrogen-bonding interactions in the transition structures of some of the reactions. Ab initio calculations were performed at the G3(MP2)-RAD//B3-LYP/6-31G(d) level of theory, and rates were obtained via variational transition state theory in conjunction with a hindered-rotor treatment of the low-frequency torsional modes. Various simplifications to this methodology were investigated with a view to identifying reliable procedures for the study of larger polymer-related systems. It appears that reasonable results may be achievable using standard transition state theory, in conjunction with ab initio calculations at the RMP2/6-311+G(3df,2p) level, provided the results for delocalized systems are corrected to the G3(MP2)-RAD level using an ONIOM-based procedure. The harmonic oscillator (HO) model may be suitable for qualitative "order-of-magnitude" studies of the kinetics of the individual reactions, but the hindered-rotor (HR) model is advisable for quantitative studies.

Journal Article↗
PubMed2006

Counter-ion perturbation of the fragmentation pathways of multiply charged anions: evidence for exit channel complexes on the fragmentation potential energy surfaces.

We report the first low-energy collisional excitation measurements and density functional theory calculations to characterize the ground state potential energy surfaces of contact ion-pair complexes that contain multiply charged anions (MCAs). Excitation of K+.Pt(CN)(4) (2-) and K+.Pt(CN)(6) (2-) result in fragmentation products associated with decay of the isolated constituent dianions, revealing that the ground state ion-pair surfaces are dominated by the intrinsic characteristics of the MCA. This observation is important since it indicates that counter-ion complexation only weakly perturbs the electronic structure of an MCA. For K+.Pt(CN)(4) (2-), where the Pt(CN)(4) (2-) dianion decays with production of two ionic fragments, we observe evidence for the existence of a novel exit-channel complex corresponding to a polar KCN salt unit bound to the Pt(CN)(3) (-) anion. The results described provide a basis for understanding the potential energy surfaces and fragmentation characteristics of other ion-pair complexes that involve MCAs.

Journal Article↗
PubMed2004

Crystal structure of a 92-residue C-terminal fragment of TonB from Escherichia coli reveals significant conformational changes compared to structures of smaller TonB fragments.

Uptake of siderophores and vitamin B(12) through the outer membrane of Escherichia coli is effected by an active transport system consisting of several outer membrane receptors and a protein complex of the inner membrane. The link between these is TonB, a protein associated with the cytoplasmic membrane, which forms a large periplasmic domain capable of interacting with several outer membrane receptors, e.g. FhuA, FecA, and FepA for siderophores and BtuB for vitamin B(12.) The active transport across the outer membrane is driven by the chemiosmotic gradient of the inner membrane and is mediated by the TonB protein. The receptor-binding domain of TonB appears to be formed by a highly conserved C-terminal amino acid sequence of approximately 100 residues. Crystal structures of two C-terminal TonB fragments composed of 85 (TonB-85) and 77 (TonB-77) amino acid residues, respectively, have been previously determined (Chang, C., Mooser, A., Pluckthun, A., and Wlodawer, A. (2001) J. Biol. Chem. 276, 27535-27540 and Koedding, J., Howard, S. P., Kaufmann, L., Polzer, P., Lustig, A., and Welte, W. (2004) J. Biol. Chem. 279, 9978-9986). In both cases the TonB fragments form dimers in solution and crystallize as dimers consisting of monomers tightly engaged with one another by the exchange of a beta-hairpin and a C-terminal beta-strand. Here we present the crystal structure of a 92-residue fragment of TonB (TonB-92), which is monomeric in solution. The structure, determined at 1.13-A resolution, shows a dimer with considerably reduced intermolecular interaction compared with the other known TonB structures, in particular lacking the beta-hairpin exchange.

Amino Acid Sequence↗
PubMed1973

Hydroxyurea-induced accumulation of short fragments during polyoma DNA replication. I. Characterization of fragments.

Hydroxyurea treatment of 3T6 mouse fibroblast cells infected with polyoma virus resulted within 15 min in more than a 20-fold reduction of the rate of both viral and cellular DNA synthesis. After the initial rapid inhibition, the rate of DNA synthesis remained essentially constant for at least 2 h. In the inhibited cells viral DNA accumulated as short chains with a sedimentation coefficient of about 4S (hydroxyurea fragments). A variable proportion of these fragments was released from the template strands when the viral DNA was extracted by the Hirt procedure. Reannealing experiments demonstrated that hydroxyurea fragments were polyoma-specific and probably synthesized on both parental strands at the replication forks.

Animals↗
PubMed2003

[Application of PCR to Haemophilus influenzae typing. I. PCR standardization for bexA gene fragment detection and for detection of DNA fragment specific for H.influenzae type B].

PCR standardization was performed in order to detect a fragment of bexA gene, which is presented in all capsulate H. influenzae isolates, and a DNA fragment specific for H. influenzae type b. Implementing of such PCR into H. influenzae typing may be very useful in cases of isolates from clinical material for which serotyping alone gives unclear results. Standardization of PCR detecting DNA fragments specific for all capsular types will enable to perform complete typing of H. influenzae isolates.

Bacterial Typing Techniques↗
PubMedDate not supplied

[Behavior of the large fragment of DNA polymerase I (the Klenow fragment) during fractionation of a cell-free extract of E. coli MRE-600].

Distribution of the DNA polymerase I large fragment (Klenow fragment) was studied during fractionation of the E. coli MRE-600 cell-free extract with polyethylenimine. On the basis of the results obtained a simple procedure is proposed that enables the Klenow fragment to be obtained as a coproduct of DNA polymerase I, RNA polymerase, polynucleotide phosphorylase, nucleotide kinases with acetokinase and nucleoside deoxy-ribosyltransferase in the framework of a combined technological scheme.

Chemical Fractionation↗
PubMed1996

The fragmentation of 510 MeV/nucleon iron-56 in polyethylene. I. Fragment fluence spectra.

The fragmentation of 510 MeV/nucleon iron ions in several thicknesses of polyethylene has been measured. Non-interacting primary beam particles and fragments have been identified and their LETs calculated by measuring ionization energy loss in a stack of silicon detectors. Fluences, normalized to the incident beam intensity and corrected for detector effects, are presented for each fragment charge and target. Histograms of fluence as a function of LET are also presented. Some implications of these data for measurements of the biological effects of heavy ions are discussed.

Algorithms↗
PubMed1996

Crystallization of a complex between the Fab fragment of a human immunoglobulin M (IgM) rheumatoid factor (RF-AN) and the Fc fragment of human IgG4.

Rheumatoid factors (RF) are the characteristic autoantibodies found in patients with rheumatoid arthritis. They recognize epitopes in the Fc region of immunoglobulin G (IgG) and are often of the IgM isotype. In order to analyse the nature of RF-Fc interactions, we have crystallized a complex between the Fab fragment of a human monoclonal IgM rheumatoid factor (RF-AN) and the Fc fragment of human IgG4. The stoichiometry of the complex within the crystals was found to be 2:1 Fab:Fc. The crystals diffracted X-rays to 0.3 nm resolution, and the space group was C2, with cell dimensions a = 16.03 nm, b = 8.19 nm, c = 6.42 nm, beta = 98.3 degrees. We have also determined the sequence of the variable region of the RF-AN light chain, not hitherto reported. This belongs to the V lambda III-a subgroup and is closely related to the germline gene Humlv318, from which it differs in three amino acid residues. This is the first reported crystallized complex between a human autoantibody and its autoantigen.

Amino Acid Sequence↗
PubMed2002

Jel44 monoclonal Fab fragment specific for HPr of the phosphoenolpyruvate:sugar phosphotransferase system of Escherichia coli and the complex of Jel44 Fab fragment with HPr: preparation, crystallization and preliminary crystallographic analysis.

Jel44 is a mouse monoclonal antibody specific for the histidine-containing phosphocarrier protein (HPr), a component of a sugar-transport system in Escherichia coli. Because Jel44 binding to HPr is dependent upon ionic strength and the enthalpic and entropic contributions do not vary over the temperature range 277-310 K, the complex is of great interest. A single crystal of the Jel44 Fab fragment was obtained and diffracted X-rays to a maximum resolution of 4.6 A on an in-house X-ray source. The crystal belongs to space group P2(1), with unit-cell parameters a = 68.6, b = 67.7, c = 105.5 A, beta = 96 degrees. Although crystals of the complex of Jel44 Fab fragment with HPr could not be fully characterized owing to suspected crystal twinning, it was encouraging that they diffracted X-rays to 2.5 A on an in-house X-ray source. It is thus foreseen that improvement of crystal quality will allow the complete solution of this novel structure.

Animals↗
PubMed2002

In vivo conversion of racemized beta-amyloid ([D-Ser 26]A beta 1-40) to truncated and toxic fragments ([D-Ser 26]A beta 25-35/40) and fragment presence in the brains of Alzheimer's patients.

The lag between beta-amyloid (A beta) deposition and neurodegeneration in Alzheimer's disease (AD) suggests that age-dependent factors are involved in the pathogenesis. Racemization of Ser and Asp in A beta is a typical age-dependent modification in AD. We have shown recently that A beta1-40 racemized at Ser(26) ([D-Ser(26)]A beta 1-40) is soluble and non-toxic to neuronal cells, but is easily converted by brain proteases to truncated toxic fragments, [D-Ser(26)]A beta 25-35/40. Furthermore, [D-Ser(26)]A beta1-40 in vivo, produced a drastic and synergistic neuronal loss by enhancing the excitotoxicity when co-injected into rat hippocampus with ibotenic acid, an excitatory amino acid, suggesting an in vivo conversion of non-toxic [D-Ser(26)]A beta1-40 to toxic fragments including [D-Ser(26)]A beta 25-35/40. In this study, we further investigated the mechanism behind the in vivo neuronal loss by [D-Ser(26)]A beta1-40 and ibotenic acid in rats, and also searched for the presence of [D-Ser(26)]A beta 25-35/40 antigens in AD brains. Quantitative analyses of the damaged area indicate clearly that non-toxic [D-Ser(26)]A beta 1-40 caused as much neurodegeneration as toxic [D-Ser(26)]A beta 25-35/40. MK-801, an NMDA receptor antagonist, completely inhibited the neurodegeneration. The immunohistochemical analyses using anti-[D-Ser(26)]A beta 25-35/40-specific antibodies demonstrated the presence of [D-Ser(26)]A beta 25-35/40 antigens in senile plaques and in degenerating hippocampal CA1 neurons in AD brains, but not in age-matched control brains. These results strengthen our hypothesis that soluble [D-Ser(26)]A beta1-40, possibly produced during aging, is released from plaques and converted by proteolysis to toxic [D-Ser(26)]A beta 25-35/40, which damage hippocampal CA1 neurons by enhancing excitotoxicity in AD. This may account for the lag between A beta deposition and neurodegeneration in AD.

Aged↗
PubMed1986

Substratum contacts and cytoskeletal reorganization of BALB/c 3T3 cells on a cell-binding fragment and heparin-binding fragments of plasma fibronectin.

BALB/c 3T3 cells make both close contacts and tight-focal contacts (with associated microfilament stress fibers) on plasma fibronectin (pFN)-coated substrata. To resolve the importance of the heparan sulfate-binding or cell-binding activities of the pFN molecule in these adhesive responses, a cell-binding fragment (120K) (CBF) free of any heparan sulfate-binding activity was prepared from human pFN by chymotrypic digestion and isolated as described by Pierschbacher et al. (Cell 26 (1981) 259). These adhesive responses to CBF were also compared to those of the model heparan sulfate-binding protein, platelet factor-4 (PF4), or heparin-binding fragments (HBF) of pFN. On intact pFN, greater than 70% of the cells formed tight-focal contacts and associated stress fibers by 4 h, the latter staining with NBD-phallacidin. In contrast, cells spread differently on CBF and failed to form tight-focal contacts; staining with NBD-phallacidin was localized to spiky projections at the cell margin with no detectable stress fiber formation. On PF4 or HBF, cells failed to form tight-focal contacts but did spread well and formed long microfilament bundles in peripheral lamellae. Spreading on CBF, HBF, or PF4 was paralleled by formation of close contacts. Spreading and to some extent attachment of cells on CBF was inhibited with a small peptide containing the Arg-Gly-Asp-Ser sequence; responses on HBF were unaffected by this peptide. When mixtures of CBF and PF4 were tested, cells still failed to form tight-focal contacts and stress fibers. These results demonstrate that the binding of CBF to its probable receptor under conditions routinely used to assay spreading activity results in an incomplete adhesive response compared with intact pFN. While this partial response may result from quantitative differences in the density of active cell-binding domains on the substratum, the pattern of microfilament reorganization produced by the binding of PF4 to cell surface heparan sulfate proteoglycans suggests that the ability of pFN to promote formation of tight-focal contacts and stress fibers may reside in the coordinate interaction of two or more binding activities in the intact molecule.

Actin Cytoskeleton↗
PubMed1989

DQA1 restriction fragment length polymorphisms and insulin-dependent diabetes mellitus: a BglII fragment labels a subset of B8,DR3 haplotypes uniquely associated with insulin-dependent diabetes mellitus.

Class II restriction fragment length polymorphism studies of 38 pedigrees with multiple cases of insulin-dependent diabetes mellitus revealed the existence of a DQA1-related polymorphism that distinguishes two kinds of HLA-B8,DR3 haplotypes. One of these, characterized by the presence of DQA1-BglII 7.20 kb, was present in all 14 examples inherited by patients and in 6 of the 12 B8,DR3 haplotypes not so inherited. The apparently complete association between the presence of this fragment and the "affected" status of B8,DR3 haplotypes (p = 0.004) was confirmed in a separate group of 26 simplex pedigrees selected for the presence of this haplotype in the respective probands (combined p less than 0.0001).

Diabetes Mellitus, Type 1↗
PubMed1995

Expression of fragment C of tetanus toxin fused to a carboxyl-terminal fragment of diphtheria toxin in Salmonella typhi CVD 908 vaccine strain.

We report the expression of fragment C of tetanus toxin (FC) fused to the eukaryotic cell binding domain (the carboxyl-terminus) of diphtheria toxin (FC-bDt fusion) in attenuated Salmonella typhi live vector vaccine strain CVD 908. The FC-bDt protein fusion was constructed using plasmid pTETnir15 which carries the gene encoding FC under control of the nirB promoter (nirBP). The open reading frame for FC was modified to incorporate an in-frame glycine-proline hinge region and a set of four restriction sites at the 3' end of the FC gene. A 482 bp DNA fragment encoding the eukaryotic cell binding domain of diphtheria toxin was then inserted at the 3' end of the modified FC gene to create an in-frame FC-bDt fusion gene. The resulting plasmid, pOG215, was able to express the FC-bDt fusion protein in both Escherichia coli DH5a and S. typhi CVD 908, as evidenced by Western immunoblots using anti-FC and anti-C-terminal diphtheria toxin monoclonal antibodies. Maximum expression of the FC-bDt fusion protein was achieved by growing CVD 908(pOG215) at the low oxidation-reduction potential of thioglycollate broth, i.e. in conditions that activate nirBP and drive transcription of the FC-bDt fusion gene. Whereas maximum expression of FC alone was also observed using thioglycollate broth, expression of bDt alone was unsuccessful using a variety of growth conditions. FC fusions constitute one strategy to "rescue" expression of proteins which are otherwise difficult to express.

Antigens, Bacterial↗