A new method of RNA preparation for detection of hepatitis A virus in environmental samples by the polymerase chain reaction

A new method based on RNA preparation from shellfish by polyethylene glycol (PEG) precipitation and trichloroacetic acid (TCA) extraction was developed for the detection of hepatitis A virus (HAV) by the polymerase chain reaction (PCR). The extraction provides high yield and the extracted RNA is undegraded. This method proved to be particularly useful for detection of RNA viruses from environmental samples by PCR.

Genetic and antigenic analyses of influenza A (H1N1) viruses, 1986-1991

Eighteen strains of human influenza A (H1N1) viruses isolated between August 1986 and January 1991 were analyzed in this study. Examination of the total viral genome of 12 strains by T1 mapping revealed that considerable genetic heterogeneity exists among these viruses. Partial sequencing of each of the non-HA RNA segments of 4 viruses having divergent T1 oligonucleotide maps indicated that only one was a reassortant virus that had genes from both the influenza A (H1N1) and (H3N2) subtypes. This reassortant obtained its PB2 gene from a virus of the H3N2 subtype and the other 7 RNA segments from an H1N1 parent. Sequencing studies of the HA1 domains of the hemagglutinin (HA) genes of these 18 strains revealed that although these viruses are antigenically similar to the reference strains A/Taiwan/1/86 and A/Singapore/6/86, 7 conserved amino acid substitutions that are shared by recently isolated H1N1 viruses have occurred in the main stream of evolution of the H1N1 subtype. Our data indicate that: (1) Genetic reassortment continues to contribute to genetic variability of H1N1 viruses. (2) Genetic variants of non-reassortant H1N1 viruses are co-circulating in the world. (3) The HA's of recent H1N1 viruses are related to those of the 1986 reference strains. (4) Although there has been little detectable antigenic variability, the HA genes of human epidemic influenza A (H1N1) viruses have continued to evolve at an evolutionary rate similar to that for the H1N1 and H3N2 viruses analyzed previously.

Role of nitric oxide synthase-containing vascular nerves in cerebrovasodilation elicited from cerebellum

We studied whether the increases in cortical cerebral blood flow (CBF) elicited by stimulation of the cerebellar fastigial nucleus (FN) are attenuated by systemic administration of inhibitors of nitric oxide synthase (NOS) and, if so, whether NOS-containing perivascular nerves arising from the sphenopalatine ganglia (SPG) are the source of NO during FN stimulation. Rats were anesthetized (1-3% halothane) and artificially ventilated. The FN or the pontine reticular formation (PRF) was stimulated electrically through a stereotaxically implanted microelectrode. To eliminate the elevation in arterial pressure (AP) elicited by FN or PRF stimulation the cervical spinal cord was transected and AP was maintained by intravenous phenylephrine. CBF was measured by a laser-Doppler probe placed over the parietal cortex. Systemic administration of the NOS inhibitor N omega-nitro-L-arginine methyl ester (L-NAME; 5-40 mg/kg) reduced resting CBF, an effect that was maximal at 10 mg/kg (-30 +/- 4%; n = 6; P < 0.003, analysis of variance). L-NAME, but not its inactive isomer D-NAME, attenuated the increases in CBF elicited by FN stimulation or hypercapnia in a dose-dependent fashion (10-40 mg/kg). At 40 mg/kg, the response to FN stimulation was reduced by 80 +/- 6% (n = 6; P < 0.05) and that to hypercapnia was reduced by 70 +/- 9% (P < 0.05). In contrast, the increases in CBF elicited by PRF stimulation were not affected (10-40 mg/kg; P > 0.05; n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)

Postreceptor events involved in the up-regulation of beta-adrenergic receptor mediated lipolysis by testosterone in rat white adipocytes

In the previous studies we have shown that testosterone increases lipolytic responsiveness to catecholamines in rat white adipocytes, and that is associated with an up-regulation of beta-adrenergic receptor density. However, the postreceptor events involved in the testosterone induced enhancement of beta-adrenergic receptor activated lipolysis in these cells have not been adequately studied, and were therefore investigated in the present study. Male Sprague Dawley rats were divided into three groups: control, castrated, and castrated treated with testosterone. The beta-adrenergic receptor-mediated cAMP accumulation, measured with RIA after isoproterenol (a beta-adrenergic agonist) stimulation was decreased in castrated rats, and reversed by testosterone treatment, suggesting a testosterone effect at or proximal to adenylate cyclase. However, no differences between the groups were found in abundance of G alpha protein messenger RNAs (G alpha s, G alpha i-1, and G alpha i-2) as analyzed by Northern blot and a solution hybridization RNase protection assay, or in G protein mass measured with a quantitative enzyme-linked immunosorbent assay in fat cell membrane preparation. Lipolysis stimulated by N6-monobutyryl-cAMP was reduced in castrated rats and recovered by testosterone treatment, suggesting that components distal to the adenylate cyclase, i.e. protein kinase A (PKA) and/or hormone sensitive lipase (HSL) also are involved in testosterone regulation of lipolysis. In conclusion, these and previous results suggest that the testosterone-induced increase in lipolytic response to catecholamines in rat white adipocytes is mediated through several events including an increased beta-adrenergic receptor density, probably an increased adenylate cyclase activity and an increased protein kinase A/hormone sensitive lipase activity at the postreceptor level with apparent absence of effect on the expression of G-proteins.

Nitric oxide synthase-containing neural processes on large cerebral arteries and cerebral microvessels

We studied whether neural processes containing nitric oxide synthase (NOS) are associated with large cerebral arteries and/or intraparenchymal microvessels. The presence of NOS-positive nerves on large cerebral arteries was examined in whole-mount preparations processed for NADPH diaphorase histochemistry, a procedure that stains NOS-containing neurons. The association between NOS-containing neural processes and intracerebral microvessels was studied by electron microscopy in ultrathin brain sections reacted with antibodies against NOS. A dense perivascular plexus of NADPH diaphorase positive axons was observed in the anterior portion of the circle of Willis and its branches while in the basilar artery the innervation was less dense. Lesions of the major sources of perivascular innervation of the cerebral arteries indicated that these nerve fibers arise from the sphenopalatine ganglia. Within the brain parenchyma, NOS immunoreactivity was observed in dendrites and axonal terminals closely associated with the basal lamina of arterioles and capillaries. We conclude that NOS-containing nerves of peripheral origin innervate large cerebral arteries while NOS-containing neural processes of central origin, especially dendrites, are closely associated with cerebral arterioles and capillaries. The presence of NOS in perivascular dendrites raises the possibility that these structures are a major source of NO during neural activity. These findings, collectively, provide morphological evidence supporting the hypothesis that NOS neurons participate in the mechanisms that match neural activity to cerebral blood flow.

Optical perceptron learning for binary classification with spatial light rebroadcasters

Binary classification of an object in a two-dimensional image is considered. A spatial light rebroadcaster is shown to be advantageous for learning in this case because it can store the weights and permit upward and downward adjustments. Two learning algorithms, based on the perceptron, are considered. A modification of the perceptron algorithm is developed so that only positive weights are needed. This is convenient because light intensity is positive only. The modified algorithm is shown to converge in a finite number of steps for positive linear separable classes. Optical experiments show the classification of four characters in two groups, in which alternative groupings are used to show robustness. In the second group of experiments the complements of the two-dimensional characters are used, and the convergence is equally fast. Adding the results from the original and complementary patterns provides a discrimination superior to that obtained using either on its own.

Requirement for posttranslational processing of Rac GTP-binding proteins for activation of human neutrophil NADPH oxidase

Rac1 and Rac2 are closely related, low molecular weight GTP-binding proteins that have both been implicated in regulation of phagocyte NADPH oxidase. This enzyme system is composed of multiple membrane-bound and cytosolic subunits and when activated catalyzes the one-electron reduction of oxygen to superoxide. Superoxide and its highly reactive derivatives are essential for killing microorganisms. Rac proteins undergo posttranslational processing, primarily the addition of an isoprenyl group to a carboxyl-terminal cysteine residue. We directly compared recombinant Rac1 and Rac2 in a human neutrophil cell-free NADPH oxidase system in which cytosol was replaced by purified recombinant cytosolic components (p47-phox and p67-phox). Processed Rac1 and Rac2 were both highly active in this system and supported comparable rates of superoxide production. Under different cell-free conditions, however, in which suboptimal amounts of cytosol were present in the assay mixture, processed Rac2 worked much better than Rac1 at all but the lowest concentrations. This suggests that a factor in the cytosol may suppress the activity of Rac1 but not of Rac2. Unprocessed Rac proteins were only weakly able to support superoxide generation in either system, but preloading of Rac1 or Rac2 with guanosine 5'-O-(3-thio-triphosphate) (GTP gamma S) restored activity. These results indicate that processing is required for nucleotide exchange but not for interaction with oxidase components.

Potential role for scavenger receptors of human monocytes in the killing of Schistosoma mansoni

Human low-density lipoproteins (LDL) bind specifically and saturably to the surface of the trematode parasite, Schistosoma mansoni, in vitro. Here we have tested whether human monocytes process the bound LDL. Monocytes obtained by leukapheresis generate H2O2, kill schistosomula, and were seen here endocytosing fluorescently labeled human LDL that was bound to the surface of the parasites. Compounds known to inhibit uptake of LDL via the scavenger receptor, namely, acetylated LDL, polyinosinic acid, dextran sulfate, fucoidan, and polyvinyl sulfate, inhibited both endocytosis of LDL and cell-mediated killing. Non-functional analogs of these inhibitors, namely, polycytidylic acid and dextran, did not inhibit either endocytosis or killing. Monocytes obtained from whole blood after venipuncture neither killed the parasite nor endocytosed LDL from the worm surface. Thus, human monocyte killing of schistosomula may involve removal of LDL from the parasite surface via scavenger receptors.

Magnesium in the active site of Escherichia coli alkaline phosphatase is important for both structural stabilization and catalysis

Site-specific mutagenesis was used to explore the roles of the side chains of residues Lys-328 and Asp-153 in Escherichia coli alkaline phosphatase. The D153H enzyme exhibits a 3.5-fold decrease in activity at pH 8.0 compared to that of the wild-type enzyme, while a double mutant D153H/K328H exhibits a 16-fold decrease in activity under these conditions. However, the Km values for both enzymes, employing the substrate p-nitrophenyl phosphate, are lower than the value for the wild-type enzyme. The Ki for phosphate, which is pH- and Mg(2+)-dependent, is decreased for the D153H enzyme and increased for the D153H/K328H enzyme. Relative to the wild-type enzyme, both mutant enzymes bind Mg2+ more weakly and undergo a time-dependent activation induced by Mg2+. The half-time of the activation process is independent of the Mg2+ concentration, indicating that the activation most probably involves a conformational change. The pH versus activity profiles of both enzymes are altered relative to that of the wild-type enzyme and exhibit greatly enhanced activity, relative to that of the wild-type enzyme, at high pH values. The pre-steady-state kinetics for the D153H and D153H/K328H enzymes exhibit a transient burst of product formation at pH 8.0, under conditions at which the wild-type enzyme exhibits no transient burst, indicating that at pH 8.0 the hydrolysis of the covalent enzyme-phosphate complex is rate-determining and not the release of phosphate from the noncovalent enzyme-phosphate complex as is observed for the wild-type enzyme. Therefore, these mutations are directly influencing catalysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of NADPH diaphorase in neurons of the rostral ventral medulla: possible role of nitric oxide in central autonomic regulation and oxygen chemoreception

We studied whether neurons containing nitric oxide synthase (NOS) are localized to the rostral ventrolateral medulla (RVM) and, if so, whether they are distinct from the adrenergic neurons of the C1 group. NOS-containing neurons and/or C1 neurons were visualized using NADPH diaphorase histochemistry and phenylethanolamine N-methyltransferase (PNMT) immunohistochemistry, respectively. A column of NADPH diaphorase-positive neurons, extending 2 mm in the rostrocaudal plane, was observed lateral to the inferior olive and medial to the C1 neurons. Double labelling studies showed that NADPH diaphorase-positive neurons were not immunoreactive for PNMT, indicating that the two enzymes were localized in the different cells. Furthermore, only a small fraction of NADPH diaphorase neurons were retrogradely labelled after injections of fluorogold into the thoracic cord. We conclude that the RVM contains a well-defined group of neurons endowed with NOS that are distinct from the adrenergic neurons of the C1 group and have only limited monosynaptic projections to the spinal cord. Since the RVM is involved in the control of arterial pressure and in oxygen-conserving reflexes, the findings raise the possibility that nitric oxide participates in central autonomic regulation and oxygen chemoreception.

Nonlinear protein binding and enzyme heterogeneity: effects on hepatic drug removal

The kinetics of substrate removal by the liver and the resulting nonlinear changes in unbound fraction along the flow path at varying input drug concentrations were examined by a model simulation study. Specifically, we varied the binding association constant, KA, and the Michaelis-Menten constants (Km and Vmax) to examine the steady state drug removal (expressed as hepatic extraction ratio E) and changes in drug binding for (i) unienzyme systems and (ii) simple, parallel metabolic pathways; zonal metabolic heterogeneity was also added as a variable. At low KA, E declined with increasing input drug concentration, due primarily to saturation of enzymes; only small differences in binding were present across the liver. At high KA, a parabolic profile for E with concentration was observed; changes in unbound fraction between the inlet and the outlet of the liver followed in parallel fashion. Protein binding was the rate-determining step at low input drug concentrations, whereas enzyme saturation was the rate-controlling factor at high input drug concentration. Heterogeneous enzymic distribution modulated changes in unbound fraction within the liver and at the outlet. Despite marked changes in unbound fraction occurring within the liver for different enzymic distributions, the overall transhepatic differences were relatively small. We then investigated the logarithmic average unbound concentration and the length averaged concentration as estimates of substrate concentration in liver in the presence of nonlinear drug binding. Fitting of simulated data, with and without assigned random error (10%), to the Michaelis-Menten equation was performed; fitting was repeated for simulated data obtained with presence of a specific inhibitor of the high-affinity, anteriorly distributed pathway. Results were similar for both concentration terms: accurate estimates were obtained for anterior, high affinity pathways; an overestimation of parameters was observed for the lower affinity posteriorly distributed pathways. Improved estimations were found for posteriorly distributed pathways upon inhibition with specific inhibitors; with added random error, however, the improvement was much decreased. We applied the method for fitting of several sets of metabolic data obtained from rat liver perfusion studies performed with salicylamide (SAM) (i) without and (ii) with the presence of 2,6-dichloro-4-nitrophenol (DCNP), a SAM sulfation inhibitor. The fitted results showed that SAM sulfation was a high-affinity high-capacity pathway; SAM glucuronidation was of lower affinity but comparable capacity as the sulfation pathway, whereas SAM hydroxylation was of lower affinity and lower capacity.

DNA sequencing of the seven remaining structural genes of the gene cluster encoding the energy-transducing NADH-quinone oxidoreductase of Paracoccus denitrificans

In our previous papers, seven structural genes (NQO1-7) of the energy-transducing NADH-quinone (Q) oxidoreductase of Paracoccus denitrificans were characterized [Xu, X., Matsuno-Yagi, A., & Yagi, T. (1991a) Biochemistry 30, 8678-8684; (1991b) Biochemistry 30, 6422-6428; (1992a) Biochemistry 31, 6925-6932; (1992b) Arch. Biochem. Biophys. 296, 40-48]. This paper reports the identification, cloning, and sequencing of seven additional structural genes in the same gene cluster (P. denitrificans enzyme complex). These seven genes, designated NQO8-14, are composed of 1038, 492, 603, 306, 2112, 1542, and 1500 base pairs, respectively. The polypeptides encoded by the NQO8-14 genes are homologous, respectively, to the ND1 product, the 23-kDa polypeptide, and the ND6, ND4L, ND5, ND4, and ND2 products of the bovine NADH-Q oxidoreductase. The order of the 14 structural genes of the Paracoccus energy-transducing NADH-Q oxidoreductase in the gene cluster is NQ07, NQO6, NQO5, NQO2, NQO1, NQO3, NQO8, NQO9, NQO10, NQO11, NQO12, NQO13, and NQO14. Downstream from the NQO14 gene an open reading frame (designated URF240) was detected which encodes a predicted polypeptide homologous to the biotin [acetyl-CoA-carboxylase] ligase of Escherichia coli. In addition, a putative terminal sequence motif was observed downstream of the NQO14 gene, suggesting that the structural gene NQO14 is the 3'-terminal gene of the Paracoccus NADH-Q oxidoreductase gene cluster. Nucleotide sequencing of the entire gene cluster revealed the presence of three unidentified reading frames: one between the NQO3 and NQO8 genes and other two between the NQO9 and NQO10 genes. These are designated URF4, URF5, and URF6 and are composed of 768, 393, and 405 base pairs, respectively. The possible functions of the putative proteins encoded by URF5 and URF6 are discussed.

GDP dissociation inhibitor prevents intrinsic and GTPase activating protein-stimulated GTP hydrolysis by the Rac GTP-binding protein

The majority of the GTP-binding proteins of the Ras superfamily hydrolyze GTP to GDP very slowly. A notable exception to this are the Rac proteins, which have intrinsic GTPase rates at least 50-fold those of Ras or Rho. A protein (or proteins) capable of inhibiting this GTPase activity exists in human neutrophil cytosol. Since Rac appears to exist normally in neutrophils as a cytosolic protein complexed to (Rho)GDI, we examined the ability of (Rho)GDI to inhibit GTP hydrolysis by Rac. (Rho)GDI produced a concentration-dependent inhibition of GTP hydrolysis by Rac1 that paralleled its ability to inhibit GDP dissociation from the Rac protein. Maximal inhibition occurred at or near equimolar concentrations of the GDI and the Rac substrate. The ability of two molecules exhibiting GTPase activating protein (GAP) activity toward Rac to stimulate GTP hydrolysis was also inhibited by the presence of (Rho)GDI. The inhibitory effect of the GDI could be overcome by increasing the GAP concentration to levels equal to that of the GDI. (Rho)GDI weakly, but consistently, inhibited GTP gamma S (guanosine 5'-3-O-(thio)triphosphate) dissociation from Rac1, confirming an interaction of (Rho)GDI with the GTP-bound form of the protein. These data describe an additional activity of (Rho)GDI and suggest a mechanism by which Rac might be maintained in an active form in vivo in the presence of regulatory GAPs.

Age-related changes in the expression of IL-2 and high-affinity IL-2 binding sites

T cell responsiveness to in vitro stimulation is severely diminished in the aged. Recent studies would suggest that this may be due, at least in part, to a reduction in interleukin 2 (IL-2) secretion and high-affinity IL-2 receptor (HA-IL-2R) expression. In this report we confirm and extend these studies to show that the fall in IL-2 production is not due to reduced numbers of IL-2 mRNA producing T cells but rather to a decline in the relative amount of IL-2 mRNA expressed per cell. Although we found an age-related reduction in the number of high-affinity binding sites on phytohaemagglutinin-activated T cell blasts by ligand-binding studies, we did not observe alterations in the number of cells that expressed both chains of the HA-IL-2R by two-colour immunofluorescence using monoclonal antibodies specific for p55 (alpha) chain and p75 (beta) chain. However, we did observe a substantial diminution in the number of activated T cells expressing p55 alone in the aged. Given that IL-2 upregulates p55 expression and is involved in the formation of HA-IL-2R, our results suggest that defective IL-2 expression is the primary lesion in age-related T cell senescence.

The presence of functional estrogen receptors in intestinal epithelial cells

Reproductive and maturational nutritive needs are examples of situations in which alterations in circulating concentrations of estrogens are associated with changes in intestinal epithelial function. However, it is not clear that any of these effects is due to direct interaction of estrogen with intestinal epithelial estrogen receptors (ER). The experiments reported here were designed to determine whether the small intestinal epithelium contains functional ER and might, therefore, be an estrogen-responsive tissue. IEC-6 cells, a non-transformed line of cells isolated from rat small intestinal crypts, were used for many of the experiments, because they provide a pure preparation of crypt epithelial cells. IEC-6 cells were found to exhibit specific saturable binding of estradiol with a Kd of 5 x 10(-10) M and approximately 100 binding sites/cell. Reverse transcriptase-polymerase chain reaction demonstrated that IEC-6 cells as well as epithelial cells from each segment of the rat intestine (duodenum, jejunum, ileum, and colon) contained ER mRNA of the sequence determined from rat uterus. Estradiol was shown to stimulate IEC-6 cell c-fos mRNA content rapidly and transiently in a manner analogous to that which has been previously demonstrated for other estrogen-responsive tissues. These data demonstrate that intestinal epithelial cells contain ER capable of regulating gene transcription and provide the basis for future studies designed to elucidate the role of estrogens in the regulation of intestinal epithelial function and pathophysiology.

A weighting method for predicting protein structural class from amino acid composition

A protein is generally classified into one of the following four structural classes: all alpha, all beta, alpha+beta and alpha/beta. In this paper, based on the weighting to the 20 constituent amino acids, a new method is proposed for predicting the structural class of a protein according to its amino acid composition. The 20 weighting parameters, which reflect the different properties of the 20 constituent amino acids, have been obtained from a training set of proteins through the linear-programming approach. The rate of correct prediction for a training set of proteins by means of the new method was 100%, whereas the highest rate of previous methods was 82.8%. Furthermore, the results showed that the more numerous training proteins, the more effective the new method.

Ablation of transplanted HTLV-I Tax-transformed tumors in mice by antisense inhibition of NF-kappa B

Mice transgenic for the human T cell leukemia virus (HTLV-I) Tax gene develop fibroblastic tumors that express NF-kappa B-inducible early genes. In vitro inhibition of NF-kappa B expression by antisense oligodeoxynucleotides (ODNs) inhibited growth of these culture-adapted Tax-transformed fibroblasts as well as an HTLV-I-transformed human lymphocyte line. In contrast, antisense inhibition of Tax itself had no apparent effect on cell growth. Mice treated with antisense to NF-kappa B ODNs showed rapid regression of transplanted fibrosarcomas. This suggests that NF-kappa B expression may be necessary for the maintenance of the malignant phenotype and provides a therapeutic approach for HTLV-I-associated disease.

[The possible role of sperm in family HBV infection]

The paper investigated HBV infectious markers in the sperm and spermatozoa of 31 male patients with hepatitis B, in the serum of their 31 spouses and 35 children respectively. HBV markers were found in 12 sperm samples, HBV-DNA was detected in 6 samples of spermatozoa (3 integrated forms and 3 free forms). The samples were hybridized repeatedly with probes of 82P labeled HBV-DNA 82P labeled lambda DNA and 82P labeled pBR822 to exclude false-positive possibility. 8 out of 12 wives (66.67%), were infected whose husband's sperm reacted positively with HBV 8 out of 14 children were infected (57.14%), whose father's sperm had HBV markers, 6 women out of 19 were infected (31.58%) whose husband's sperm did not react with HBV, 11 of 22 children were infected (50%). The investigation found that the HBV in sperm was higher in the patients with HBeAg positive serum. The wives were easier infected from husbands with HBV positive sperm. The result suggested that sperm must be one of medium of HBV transmission. HBsAg HBeAg anti-HBc HBV-DNA were found in the serum sample of one 4 month infant, with no anti-HBc-IgM. His mother was negative in HBV. The integrated form HBV-DNA was detected in his father's spermatozoa. The transmission between father and son is perhaps mainly by contact each other daily. If HBV has the possibility of vertical transmission is to be studied.

Effects of cigarette smoking on rate of loss of pulmonary function in adults: a longitudinal assessment

Data from a random sample of 8,191 men and women selected in six U.S. cities and examined on three occasions over a 6-yr follow-up period were analyzed by longitudinal methods to describe the effects of smoking history and current smoking behavior on rate of loss of pulmonary function during adult life. Former smokers had age- and height-adjusted rates of decline (34.3 ml/yr for men and 29.6 ml/yr for women) comparable with those of never smokers (37.8 ml/yr for men and 29.0 ml/yr for women) but much smaller than those of continuing smokers (52.9 ml/yr for men and 38.0 ml/yr for women). The accelerated rate of loss of FEV1 among smokers depended linearly on the number of cigarettes smoked per day during the interval between examinations. The estimated increase in rate of loss associated with smoking was 12.6 ml/yr per pack/day for men and 7.2 ml/yr per pack/day for women. These longitudinal estimates of the effects of smoking were approximately 50% larger than estimates obtained from cross-sectional analysis of the initial pulmonary function examination. Men who started smoking had accelerated rates of loss (55.9 ml/yr) as did women (43.1 ml/yr). Smokers who stopped smoking between examinations had reduced declines (41.2 ml/yr for men and 28.7 ml/yr for women) compared with continuing smokers. The age-specific rates of loss suggest that the benefits of cessation may be greatest among the youngest smokers.(ABSTRACT TRUNCATED AT 250 WORDS)

Infrared Reflection-Absorption Spectroscopy and STM Studies of Model Silica-Supported Copper Catalysts

The structure of model silica-supported copper catalysts has been investigated with scanning tunneling microscopy (STM) and infrared reflection-absorption spectroscopy (IRAS). The IRAS studies of CO on the model silica-supported copper catalysts indicate that there are several types of copper clusters with surface structures similar to (111), (110), and other high-index planes of single-crystal copper. The STM studies show several types of copper clusters on silica and reveal images of metal clusters on an amorphous oxide support with atomic resolution.