bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and ligand‐binding modes of human serum albumin studied by UV resonance raman spectroscopy
Authors: Hashimoto Shinji , Yabusaki Takahiko , Takeuchi Hideo , Harada Issei 
Published: May 2005

AbstractUltraviolet resonance Raman spectra have been measured for human serum albumin (HSA) and its complexes with three types of ligands. Tyr and Trp Raman bands of ligand‐free HSA are strongly enhanced with 240‐nm excitation compared with those of aqueous amino acids, indicating that the side chains of some Tyr residues and the unique Trp at position 214 are hydrogen bonded in hydrophobic environments. The high intensity of Tyr and Trp Raman scattering remains unchanged in a wide pH range of 3.5–9.0 and the microenvironments of the Tyr and Trp residues seem conserved in this pH range. The Tyr Raman intensity of HSA increases upon binding of palmitic acid, indicating hydrophobic interactions between the Tyr phenol ring and the aliphatic chain of the bound fatty acid. Binding of warfarin, on the other hand, does not affect the Tyr Raman intensity. Instead, an increase is observed for the Raman intensity of Trp‐214, which is located at the opening of the warfarin binding site. Concomitantly a conformation‐marker Raman band of Trp‐214 changes in frequency and the warfarin Raman intensity increases, suggesting direct hydrophobic interactions between Trp‐214 and warfarin. Complexation of ibuprofen and HSA increases the Raman intensity of Tyr but not of ibuprofen, which is ascribed to the formation of a hydrogen bond between the carboxylate of ibuprofen and the phenolic OH of Tyr‐411, the unique Tyr residue at the ibuprofen binding site. Hydrophobic interactions and hydrogen bonding of Tyr and Trp residues play a key role in ligand binding of HSA. © 1995 John Wiley & Sons, Inc.
Localized electron polarization in a substrate analog binding to the active site of enoyl‐CoA hydratase: Raman spectroscopic and conformational analyses of rotamers of hexadienoyl thiolesters
Authors: Tonge P. J. , Anderson V. E. , Fausto R. , Kim M. , Pusztai‐Carey M. , Carey P. R. 
Published: May 2005

AbstractThe Raman bands associated with different rotamers of hexadienoyl ethyl thiolester, CH3CHCHCHCHC(O)SCH2CH3, have been partially assigned using recent conformational and vibrational spectroscopic analyses of ethyl thiocrotonate CH3CHCHC(O)SCH2CH3.1 In particular, rotational isomers involving the CHC(O) and SCH2 axes have been characterized. The assignment of the vibrational modes of different conformers of hexadienoyl ethyl thiolester was further facilitated by variable‐temperature (+20°C to −90°C) Raman studies on the neat thiolester. High‐quality Raman spectra of hexadienoyl‐coenzyme A bound to the enzyme enoyl‐CoA hydratase were obtained using 647.1‐nm excitation and Raman difference spectroscopy. The findings provided by analysis of the ethyl thiolester model compound enable us to conclude that conformational selection occurs for the CoA analog upon binding, resulting in the presence of a single‐rotamer population in the hexadienoyl moiety on the enzyme. The hexadienoyl‐CoA was labeled with 18O in the CO group and, separately, with 13C at the C2 position. A comparison of Raman data for the free and bound ligands, isotopically labeled and unlabeled, indicates that strong π‐electron polarization occurs in only a part of the hexadienoyl chain, viz, in the CCCO fragment, upon binding. The polarization gives rise to important contributions from canonical (resonance) forms of the type C+CCO−. In contrast, the C4C5 linkage (where the carbon atom numbering is C6C5C4C3C2C1O) seems little perturbed in the bound ligand. The causes and mechanistic advantage of the observed localized polarization are discussed. © 1995 John Wiley & Sons, Inc.
Modeling the heme vibrational spectrum: Normal‐mode analysis of nickel (II) etioporphyrin‐I from resonance raman, ft‐raman, and infrared spectra of multiple isotopomers
Authors: Hu Songzhou , Mukherjee Arka , Piffat Christine , Mak Ronald S. W. , Li Xiao‐Yuan , Spiro Thomas G. 
Published: May 2005

AbstractNearly complete vibrational assignments have been obtained for a heme model, nickel etioporphyrin‐I (NiEPI), using variable‐wavelength resonance Raman (RR), and FT‐Raman (FT‐R), as well as infrared (IR) spectroscopy, on a series of isotopomers labeled at positions in the skeleton (15N, β‐13C, meso‐d4, 15N‐meso‐d4) and in the peripheral substituents (methyl‐d12, ethyl‐d8, and ethyl‐d12). The vibrational bands are assigned to the porphyrin skeletal and substituent modes on the basis of the mode description scheme developed for nickel octaethylporphyrin (NiOEP) with the aid of a normal‐mode analysis of NiEPI, explicitly including the peripheral substituents, i.e., the methyl and ethyl groups. The previously reported NiOEP force field was refined to account for the observed isotope shifts of NiEPI isotopomers. An important result is the requirement of relatively large, long‐range force constants for methine bridge bonds on opposite sides of the porphyrin ring. These 1–8 and 1–9 interaction force constants are required to reproduce the frequencies and isotope shifts of six Cα‐Cm stretching modes and especially to predict the relative order of the two highest‐frequency Eu modes, v(Cα‐Cm) (v38, ∼ 1570 cm−1) and v(Cβ‐Cβ) (v37, ∼ 1600 cm−1). Most of the substituent (methyl and ethyl) vibrations are located in the RR and IR spectra. Strong RR enhancement of some substituent modes can be attributed to hyperconjugative interaction of the aliphatic groups with the porphyrin a1u orbital, as well as vibrational mixing of substituent modes with the nearby skeletal modes. © 1995 John Wiley & Sons, Inc.
Fluorescence line narrowing study of the ground‐state and first‐excited‐state vibrational frequencies of Sn and Zn cytochromes c
Authors: Laberge Monique , Vanderkooi Jane M. 
Published: May 2005

AbstractFluorescence‐line‐narrowing (FLN) spectra are presented for Sn cytochrome c (Snc) obtained under Q0‐0 and Q0‐1 excitation and for Zn cytochrome c (Znc) under Q0‐1 excitation. Vibrational frequencies of the ground and first excited states are reported for Snc. Additional excited‐state Znc frequencies are also presented, thus contributing to a previous FLN Znc investigation. The spectra of Snc shows more phonon broadening than for Znc, but vibrational frequencies of the S0 and S1 states could be obtained and the distribution function of the 0, 0 transition was determined. Snc and Znc showed good agreement in their excited‐state vibrational frequencies. Some S1 vibrational frequencies of Znc are seen to downshift with respect to ground‐state vibrations, suggesting that the porphyrin S0 to S1 expansion observed in other porphyrin systems also occurs in cytochrome c derivatives. © 1995 John Wiley & Sons, Inc.
Plasma ornithine carbamyl transferase level as an indicator of ischaemic injury of rat liver
Authors: Frederiks Wilma M. , Vogels Ilse M. C. , Fronik Gerard M. 
Published: May 2005

AbstractThe activity of ornithine carbamyl transferase (OCT) and glutamate pyruvate transaminase (GPT) in serum has been correlated with the extent of necrosis 24 h after different periods of ischaemia in rat liver. The extent of necrosis has been quantified as the volume density of necrosis in the total ischaemic liver lobes using tetranitro BT. The GPT‐activity in serum is maximal between 1 and 5 h after different periods of ischaemia, whereas OCT reaches its maximum between 5 and 12 h after ischaemia. The total amount of leaked enzyme‐activity as well as the peak value give a linear correlation with the extent of necrosis for OCT and GPT. There is a differnece between the character of these two enzymes in that a small leakage of GPT does not indicate liver cell necrosis later on. However, the appearance of OCT in the blood, an enzyme localized in the mitochondrial matrix, has a predictive value for the extent of necrosis, likely to occur later on. GPT, an enzyme from the cytoplasm, can also occur in the blood during the reversible stage of liver cell damage.
Quantitative and qualitative changes of plasma membrane glycoproteins in the early period of liver regeneration
Authors: Enrich C. , Bachs O. , Rius E. , Serratosa J. , Domingo J. 
Published: May 2005

AbstractAlterations of cell surface glycoconjugates have been observed in many developing systems and may be important in the physiological control of growth and differentiation. Liver regeneration after partial hepatectomy is a suitable model in which to study the regulatory mechanisms of cell proliferation in vivo. We have isolated the sinusoidal plasma membrane of hepatocytes at different times after partial hepatectomy. The sialic acid content and the SDS‐polyacrylamide gel electrophoresis pattern of glycoproteins were determined. A decrease of periodic acid‐Schiff‐profiles, a change in the binding capacities of 125I‐concanavalin A, a reduction of the sialic acid content and the appearance and disappearance of specific components have been observed during the pre‐replicative phase of liver regeneration. These findings during this early period are consistent with the active involvement of the plasma membrane glycoproteins in the transition of cells to the proliferative state.
Sulfur‐containing amino acids that increase renal glutathione protect the kidney against papillary necrosis induced by 2‐bromoethylamine
Authors: Thielemann L. E. , Oberhauser E. W. , Rosenblut G. , Videla L. A. , Valenzuela A. 
Published: May 2005

AbstractPapillary necrosis was observed in the kidneys of rats, 72 h after receiving a single injection of bromoethylamine (BEA). This effect was associated with renal glutathione (GSH) depletion 1 h after the administration of BEA. Stimulation of renal GSH synthesis by pretreatment of the animals either with glutamine + glucine + cystine or N‐acetyl‐L‐cysteine was attempted. Low doses of these precursors administered previously to BEA, respectively, decreased or abolished the GSH depletion. Nevertheless, both pretreatments failed to modify the magnitude of renal papillary necrosis. High doses of these precursors did not modify the BEA‐induced GSH depletion, but they significantly increased GSH levels 24 h after BEA administration. At this time, although a smaller intensity of renal papillary necrosis was observed with the amino acid mixture pretreatment, N‐acetyl‐L‐cysteine pretreated rats showed no papillary necrosis. It is suggested that the observed protective effects against BEA‐induced renal papillary injury may be ascribed in some measure, to a mechanism independent of GSH.
Lack of inhibition of vasopressin‐stimulated Na+K+ATPase by atrial natriuretic factor in the rat renal medullary thick ascending limb of Henle's loop
Authors: Charlton Judith A. , Baylis Peter H. 
Published: May 2005

AbstractThe anti‐diuretic hormone, arginine vasopressin (AVP) stimulates the activity of Na+K+ATPase in the rat renal medullary thick ascending limb of Henle's loop (mTAL). Atrial natriuretic factor (ANF) has been suggested to exert a tubular effect on the mammalian nephron, perhaps in part, by interacting with other hormones. In the present study, we investigated the effect of rat ANF with and without AVP upon mTAL Na+K+ATPase activity using cytochemical methods. ANF alone failed to inhibit or stimulate Na+K+ATPase activity in mTAL at any of the concentrations tested (10 nmol–0·1 pmol l−1). Unlike the rat hypothalamic digitalis‐like factor, ANF (10 nmol–10 fmol l−1) did not inhibit Na+K+ATPase activity after stimulation with AVP (l fmol l−1) for either 4 or 10 min. The results suggest that ANF does not exert an effect on mTAL, either alone or in conjunction with AVP.
Studies of the regulation of renal gluconeogenesis in normal and Pi depleted proximal tubule cells
Authors: Nakagawa Takeshi , Butterworth Peter J. 
Published: May 2005

AbstractPi depletion of proximal tubule cells isolated from mouse kidney results in a decrease in the cell content of fructose‐2,6‐bisphosphate and an increase in the rate of gluconeogenesis from pyruvate, malate and succinate. Gluconeogenesis from glycerol is unaffected by Pi depletion. Introduction of fructose‐2,6‐bisphosphate into the cytosol of ATP‐permeabilized cells is accompanied by a fall in gluconeogenesis.The presence of external Ca2+ stimulates gluconeogenesis. When cytosolic Ca2+ is raised to 1·8 μM by permeabilization, the resealed cells still require 2·5 mM Ca2+ in the bathing medium in order to perform gluconeogenesis at the maximum rate. Cells permeabilized in the presence of cAMP show a decreased rate of glucose production. Phorbol ester stimulates gluconeogenesis provided that the phorbol treatment is performed in the absence of Ca2+ ions.It is suggested that Pi depletion may stimulate pyruvate carboxylase activity and facilitate the entry of certain gluconeogenic substrates into mitochondria. It is also proposed that important aspects of the control of renal gluconeogenesis by parathyroid hormone are mediated by protein kinase C.
Evidence of the receptor nature of the binding sites induced in tetrahymena by insulin treatment. A quantitative cytofluorimetric technique for the study of binding kinetics
Authors: Kovács P. , Csaba G. 
Published: May 2005

AbstractTetrahymena pyriformis GL cells pretreated (imprinted) and not pretreated with insulin showed dissimilar quantitative relations of FITC‐insulin binding. Displacement of FITC‐insulin by unlabelled insulin was considerably less in the control than in the imprinted series. The curve for saturation of the binding sites with FITC‐insulin resembled a true saturation curve. The imprinted cells bound considerably more hormone in a shorter time than the control cells at identical levels of exposure. The dissociation of bound hormone from the imprinted cells increased over the control at 23°C, and to a still greater degree at 4°C. The effect of the pH of the medium on the dissociation of bound FITC‐insulin also differed between the imprinted and not imprinted cells. Thus the proposed cytofluorimetric assay of binding kinetics demonstrated the actual conditions of receptor activity, and indicated that the induced insulin binding sites of Tetrahymena behaved similarly to ‘classical’ receptors.
Temporal adaptation of human neutrophil metabolic responsiveness to the peptide formylmethionyl‐leucyl phenylalanine: A comparison between human neutrophils and granule‐depleted neutrophil cytoplasts
Authors: Dahlgren Claes 
Published: May 2005

AbstractWhen polymorphonuclear leukocytes (neutrophils) and soluble or particulate matter interact, the cells produce superoxide anions (O2−) and hydrogen peroxide (H2O2). The chemotactic peptide formylmethionyl‐leucylphenylalanine (FMLP) induced a very weak response in normal neutrophils. The cellular response was changed, however, as a result of in vitro aging of the cells, i.e. the magnitude of the response was increased following storage of the cells at 22°C for up to 120 min, in the absence of any stimulus, and before the addition of the peptide. When phorbol myristate acetate was used as a stimulus, there was a pronounced production of O2− and H2O2, but no change in magnitude as a result of in vitro aging. When neutrophil cytoplasts (granule‐free vesicles of cytoplasm enclosed by plasmalemma) were exposed to the peptide FMLP of PMA, the vesicles produced both O2− and H2O2. There was, however, no increase in oxidative metabolite production in cytoplasts as a result of in vitro aging when either FMLP or PMA was used as a stimulus. The results thus indidate that mere incubation at room temperature primed the cells to increase their production of oxidative metabolites as a result of spontaneous exposure of hidden receptors. The fact that no such effects were observed with cytoplasts indicates that spontaneous receptor recruitment is a granule‐dependent process.
The inhibitory effect of neonatal rat smooth muscle cells and elastic extracellular matrix on development of the newly seeded cell population in culture
Authors: Hausmann J. , Horáčková J. , Krausová J. , Verbitzki V. 
Published: May 2005

AbstractNeonatal smooth muscle cells were seeded in standard plastic Falcon flasks, on top of another 2‐month‐old culture of the same cell population or on top of an acellular matrix prepared by removal of these cells. The effect of both complete and acellular layers on the production of elastin, collagen and total extracellular matrix (EM) proteins as well as on cell division was measured. Compared with the standard population grown on plastic, the complete cell layer almost completely prevented the newly seeded cells from dividing. The acellular matrix did not affect cell doubling but caused a distinct decrease in the production of EM components.
Activation of phospholipase A2 by 1,25 (OH)2 vitamin D3 and cell growth in monocytic U937 and mono mac 6 cells
Authors: Aepfelbacher Franz C. , Weber Peter C. , Aepfelbacher Martin 
Published: May 2005

AbstractSoluble phospholipase A2 activity was characterized in two human monocytic cell lines, U937 and Mono Mac 6. The enzyme showed an absolute requirement for Ca++, an alkaline pH optimum and Michaelis‐Menten kinetics in both cell lines. Differentiation of U937 and Mono Mac 6 cells with 1,25 (OH)2 vitamin D3 (10 nM, 72 h) enhanced PLA2 activity by 82 per cent and 56 per cent, respectively. Furthermore, kinetic experiments revealed that enzyme activity increased within 3 h when cells were brought from the nonproliferative phase of growth to the start of a new cycle of cell proliferation. This initial activation of PLA2 could be inhibited by cycloheximide and actinomycin D, indicating the requirement of gene transcription. Taken together, these results suggest a role of cytosolic, Ca++‐dependent PLA2 in differentiation and growth of monocytic cells.
Guinea pig peritoneal macrophages. Differential effects of lectins on interaction with IgG immunoglobulins
Authors: Sokal Izabela , Kułacz Agata , Gorczyca Wojciech , Janusz Maria , Lisowski Jozef 
Published: May 2005

AbstractGuinea pig peritoneal macrophages have on their surface two receptors, one (Fcγ1/γ2R) binding both guinea pig IgG1 and IgG2 and the second (Fcγ2R) binding only IgG2 immunoglobulins. We have previously shown that treatment of macrophages with neuraminidase or glycosylation inhibitors affects, in a different way, the binding of guinea pig IgG1, IgG2, and rabbit IgG. In the present study we have shown that pretreatment of guinea pig macrophages with lectins (Con A, WGA, and PNA) also has a different effect on the interaction of the cells with IgG. The lectins increased the binding of guinea pig IgG1, whereas rabbit IgG and guinea pig IgG2 were bound with a lower efficiency than in the case of control cells. Since sialic acid residues seem to modulate the activity of receptors and WGA interacts with sialylated oligosaccharides, we determined the IgG‐binding characteristics for WGA‐pretreated macrophages. We found that the increase in IgG1‐binding ability was caused by an increase in the value of Kapp, but the number of IgG‐binding sites was lower than in the control cells. In the case of rabbit IgG and guinea pig IgG2 we observed a decrease of both the value of Kapp and the number of IgG‐binding sites. WGA did not interact directly with the Fcγ receptor. The results of our former papers and the different effects of lectins of various specificities described in this paper suggest different positions of Fcγ1/γ2 and Fcγ2R in the plane of the plane of the macrophage membrane in respect to various membrane glycoconjugates. Interaction of IgG with macrophage Fcγ receptors depends in a different way on glycoconjugates on the surface of the macrophage. Our results suggest that changes in glycosylation of macrophage surface glycoconjugates may be used by the cell for regulating the binding activities of the macrophage Fcγ receptors.
Platelet glycohydrolase activities: Characterization and release
Authors: Emiliani Carla , Martino Sabata , Orlacchio Antonio , Vezza Roberta , Nenci Giuseppe G. , Gresele Paolo 
Published: May 2005

AbstractGranules containing acid hydrolases have been detected in human platelets but have not been thoroughly characterized.We have studied the activity and characteristics of glycohydrolases present in normal human platelets, evaluated their release upon stimulation with thrombin, and assessed the contribution of platelet ‐ released lysosomal contents to the glycohydrolase activity present in normal serum. Platelets contained a remarkable glycohydrolase activity with a prevalence of β ‐ N‐acetylhexosaminidase. All glycohydrolases were released to some extent upon stimulation with thrombin and contributed to the glycohydrolase activity found in human serum. α‐Mannosidase and α‐galactosidase were partially inactivated after release by a mechanism as yet undefined. In addition, thrombin stimulation affects the intraplatelet isoenzyme pattern of β‐N‐acetylhexosaminidase by producing the appearance of a new form.
Experimental design in chemometrics
Authors: Deming Stanley N. , Palasota John A. , Palasota Josephine M. 
Published: May 2005

AbstractChemometrics is defined as the application of mathematical and statistical methods to chemical systems. Systems theory is seen to be useful for organizing and categorizing the inputs to and outputs from chemical systems. Advances in measurement science in the 1950s and 1960s, particularly in analytical chemistry, created a need for a multivariate approach to data analysis. Early chemometrics emphasized the use of structure‐finding methods for existing data sets. In many instances, data sets can be obtained from designed experiments. Such data sets are more likely to contain the desired information and the data can usually be acquired at less cost. Renewed interest in statistical process control will provide many new, more robust data sets in the future.
The quality of mean and variance estimates for normal and lognormal data when the underlying distribution is misspecified
Authors: Blackwood L. G. 
Published: May 2005

AbstractTheoretical and simulation results are employed to evaluate mean and variance estimates for normal data when a lognormal distribution is assumed and for lognormal data when a normal distribution is assumed. Misspecifying the distribution leads to the use of suboptimal estimation methods. However, the results show that the suboptimal methods still produce estimators of good quality (low bias and variance) relative to the minimum variance unbiased estimators for each distribution, at least when practical efficiency is considered.
Comparison of two screening methods for the detection of volatile organic compounds in ground water
Authors: Rajagopal R. , Li Ping‐Chi 
Published: May 2005

AbstractIt is shown that the presence of 31–35 commonly measured volatile organic compounds (VOCs) in ground water can be detected with small error rates by using screening methods which analyze for a subset of such VOCs. A study of selected data sets indicates that analytical determinations of only from two to eight VOCs will suffice to detect 95% of all VOC hits. It is also shown that a serially optimal algorithm for selecting the VOCs for screening is very nearly as accurate as a globally optimal algorithm and much easier to implement. These conclusions are supported by empirical evidence from two drinking‐water data sets and one hazardous waste site data set. Additional research areas are also outlined.