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At least 415 records · Page 23Linked to original sources
PubMed2001

Dilution of the 75-g oral glucose tolerance test improves overall tolerability but not reproducibility in subjects with different body compositions.

Poor reproducibility of the 75-g oral glucose tolerance test (75-g OGTT) is a major criticism. To test whether dilution might be a contributor, we studied the effect of administering it at 300, 600, and 900 ml on the coefficient of variation (CV) and overall tolerability. Each dilution was randomly repeated three times by 35 subjects: 11 lean (body fat [BF]: 11.5+/-1.5%, body mass index (BMI): 24.1+/-0.8 kg/m(2), age: 33+/-3 years), 12 normal (BF: 24.3+/-1.3%, BMI: 23.9+/-0.7 kg/m2, age: 33+/-3 years), and 12 obese (BF: 34.1+/-1.5%, BMI: 34.5+/-1.6 kg/m(2), age: 41+/-4 years). The protocol followed, the American Diabetes Association (ADA) guidelines with venous samples drawn at 0, 15, 30, 45, 60, 90, and 120 min. Scales assessing palatability, acceptability, satiety, nausea, and dizziness were also completed. No differences were detected in CV between the three dilutions at the 2 h-diagnostic-endpoint in any group. CV for glycemia, however, was lower for the 300-ml OGTT (10+/-2.1%) than either the 600 ml (17.9+/-2.1%) or 900-ml OGTT (19.9+/-4.4%) at 45 min in the lean group (P<0.05). CV for insulinemia was lower for the 300 ml (30.6+/-4.5%) and 600 ml (30.6+/-4.1%) OGTT than the 900-ml OGTT (53.7+/-7.9%) at 60 min in the obese group (P<0.05). When affective ratings were compared, the 600-ml OGTT scored highest on palatability and acceptability (P<0.05). We concluded that the dilution of the 75-g OGTT improves the overall tolerability but not reproducibility of results. Practitioners may choose to give it at the best-tolerated dilution.

Adult↗
PubMed1987

Selection of milks with varying fat contents and related overall liking, attitudes, norms and intentions.

A total of 236 subjects who used non-fat (0%), low-fat (1.9%) or regular-fat (3.9%) milk as their principal milk source participated in a hedonic test and in a survey in which overall liking, attitudes, norms and buying intentions of the three milk types as well as aspects of their consumption and shifts among them were studied. The subjects strongly preferred their own milk type in hedonic tests, in survey ratings of liking, and in their beliefs concerning sensory quality, nutritional and health value and suitability for various purposes. All the user groups indicated a reluctance to shift from the usual milk type but were, however, aware of nutritional recommendations as to which milk type they should use. The Fishbein model of attitudes, norms and behaviour explained 18-47% of the variation in buying intentions or selections of the milk types. The predictive power of the attitudinal component was greater than that of the norm component. Insertion of survey ratings of overall liking into the regression model slightly improved its predictive power (up to 25-48%), but this component was highly correlated with the attitude variable. It is concluded that the use of a certain milk type is highly supported by a consistent belief structure and positive attributions, which defend the established behaviour against any pressure to shift to another type of milk.

Adult↗
PubMed2001

The risk of second malignant tumors and its consequences for the overall survival of Hodgkin's disease patients and for the choice of their treatment at presentation: analysis of a series of 1524 cases consecutively treated at the Florence University Hospital.

PURPOSE: To quantify the incidence of second malignant tumors (SMT) as a whole and that of second "solid" tumors (SST) and leukemia (L) in a large series of 1524 Hodgkin's disease (HD) patients (pts) treated at the Florence University Hospital (UFH); to define the clinical and therapeutic features possibly related with SMT occurrence; to evaluate the consequences of SMT for the overall survival of the series studied and for the choice of the treatment of HD at presentation. METHODS AND MATERIALS: From 1960 to 1991, 1524 pts with HD, Clinical Stage (CS) I--IV have been treated at the UFH. Overall treatment consisted of radiation alone (RT, 36%), chemotherapy alone (CHT, 21%), or both (RT + CHT, 43%). The cumulative probability (CP) of SMT, SST, and L was calculated for the whole series and for the different clinical and therapeutic subgroups, and the results compared with uni- and multivariate analysis ("internal" comparison, IC). Standardized incidence ratios (SIR) for different SMT types (estimated on the basis of gender, age, period specific incidence rates of the general population) have been also calculated ("external" comparison, EC). The impact of the SMT-related mortality on the survival of the entire series has been estimated. RESULTS: A 14.9% 20-year CP of SMT was registered, along with a SIR of 2.04 (95% confidence interval [CI]: 1.2--2.5). Both IC and EC showed a statistically significant relationship between L incidence and treatment with CHT, alone or in combination with RT. A significant excess of breast cancers has been observed in RT-treated patients with longer follow-up (SIR, 2.9); an excess of other common SST (lung, non-Hodgkin's lymphomas) is evident in pts treated with either RT, RT + CHT, or CHT. The actuarial long-term survival of the series would have been better of about 3%, in absence of the SMT mortality possibly due to HD treatment, which is almost equally divided between patients treated with RT alone, CHT alone, and RT + CHT. CONCLUSIONS: SMT represent an important late event in HD long-term survivors. The relationship between L and treatment with CHT seems to be the most clearly defined. The effect of SMT on the survival of the entire series, although not negligible, does not seem to justify by itself substantial alterations in the current standards for the treatment of HD at presentation.

Adult↗
PubMed2003

Postoperative radiotherapy in squamous cell carcinoma of the oral cavity: the importance of the overall treatment time.

PURPOSE: To test the hypothesis that (1) the distinction between intermediate- and high-risk patients by clustering different prognostic factors results in a significant difference in treatment outcome and (2) a shorter interval between surgery and radiotherapy and shorter overall treatment times of radiation (OTTRT) result in higher rates of locoregional control (LRC). METHODS AND MATERIALS: Included were patients (n = 217) with previously untreated squamous cell carcinoma of the oral cavity treated with radical surgery and postoperative radiotherapy. Patients with extranodal spread or microscopic residual disease and patients with two or more other risk factors (i.e., N2b-N3, >1 nodal level involved, perineural growth, or stage T3-T4) were classified as high-risk patients. Patients with only one other risk factor were classified as intermediate risk. RESULTS: In the intermediate-risk group, the 3-year LRC was 87% as compared with 66% in the high-risk group (p = 0.0005). No association was found between interval and LRC. However, the OTTRT was significantly associated with LRC. The 3-year LRC was 87%, 75%, 69%, and 51% when the OTT was <6 weeks, 6-7 weeks, 7-8 weeks, and >8 weeks, respectively (p = 0.0004). The 3-year overall survival (OS) in the intermediate risk patients was 74% compared with 50% in the high-risk group (p = 0.0014). A significant association was also found between the OS and OTTRT. The OS increased from 50% when the OTTRT was >8 weeks to 74% when the OTT was <6 weeks (p = 0.006). Similar results were found with regard to the disease-free survival (DFS). In the multivariate analysis, both risk group and OTT were significantly associated with LRC, DFS, and OS. No significant interaction term was present between these two factors, which means that the OTT was of importance both for the high-risk and the intermediate-risk patients. CONCLUSION: In the subset of patients with carcinoma of the oral cavity, the classification of high- and intermediate-risk patients by clustering a number of prognostic factors provides important prognostic information regarding LRC, DFS, and OS. The OTT was the most important prognostic factor both in the high-risk and intermediate-risk patients. Reducing the OTT to 6 weeks or less is a rather simple measure to achieve a considerable improvement of the outcome of treatment in this category of patients.

Adult↗
PubMed2002

Does the histological subtype of high-grade central osteosarcoma influence the response to treatment with chemotherapy and does it affect overall survival? A study on 570 patients of two consecutive trials of the European Osteosarcoma Intergroup.

Large randomised trials are mandatory when one wants to examine the effects of different aspects (such as the treatment modality) of a pathological condition on the overall outcome. This is especially true when studying a disease in which there is a multifactorial influence on progression and outcome such as osteosarcoma. Data on 570 patients with biopsy-proven primary central osteosarcoma of an extremity included in two consecutive studies of the European Osteosarcoma Intergroup (EOI) were analysed in order to evaluate if the histological subtype of the biopsy specimen correlated with the subtype of osteosarcoma represented in the resected specimen, if there was a relationship between the histological subtype and overall survival and if there was a relationship between the histological subtype and histological response to chemotherapy. High-grade osteosarcoma, as defined by established criteria, was subtyped as either conventional, chondroblastic, teleangiectatic, small cell, fibroblastic, osteoclast rich, anaplastic and sclerotic/osteoblastic well differentiated. A panel of experienced pathologists with a special interest in bone pathology was appointed to review the histological diagnosis and to assess the tumour response to chemotherapy on the resected specimen of each patient entered into the trials. Subtyping on the biopsy specimen proved to be highly representative for the subtype of the whole tumour. In 102 patients for which subtyping was performed on the biopsy and the resected specimens, there were only two discrepancies. Of the 568 patients for whom subtype was available, 404 (71%) were of the conventional type, 54 (10%) were chondroblastic, 53 (9%) had fibroblastic tumours and the remainder consisted of rare subtypes. A good response to preoperative chemotherapy was defined as 90% or more necrosis. The proportion of patients responding well to chemotherapy differed significantly between subtypes (Chi-square test statistics=11.44, P=0.01 on 3 degrees of freedom (d.f.)). In comparison with the conventional subtype, there was a higher proportion of good responders in the fibroblastic group and a lower proportion of good responders in the chondroblastic group. Good responders had a significantly better survival than patients who responded poorly to the pre-operative chemotherapy (logrank statistic=25.20, P<0.01 on 1 df). Survival did not differ significantly according to subtype (logrank statistic=2.72, P=0.44 on 3 df), although there was a suggestion that patients with chondroblastic tumours experienced a better long-term survival. This large set of prospectively-collected data provides important information on the relationship between pathological subtype, histological response and survival. Histological response has a known prognostic effect on survival, and we have shown that the rates of response differ by subtype. There is some evidence from this study that the specific histological subtypes, i.e. the chondroblastic subtype, experience better survival. However, despite this large multi-institutional study, we have insufficient numbers of non-conventional tumours to examine this unambiguously for these subsets.

Adolescent↗
PubMed2002

Use of high-dose cytarabine to enhance cisplatin cytotoxicity-effects on the response and overall survival rates of advanced head and neck cancer patients.

UNLABELLED: It has been reported that cytarabine, acting by at least two different mechanisms, enhances the cytotoxic effect of cisplatin in in vitro systems. The aim of this open, prospective, randomised study was to estimate the eventual benefits from the inclusion of high-dose cytarabine in the cisplatin-5-fluorouracil (5-FU) regimen as first-line treatment of patients with advanced head and neck cancer. The study recruited successive patients with unresectable grade I/II head and neck cancer who were not suitable for irradiation treatment (T any N3 or T4 N2C), metastatic or previously irradiated. All patients gave their informed consent. A joint ear, nose and throat (ENT) oncological committee performed the selection. A total of 170 patients were included in the study. Patients randomised to arm A were given 1000 mg/m(2) cytarabine on day 1 preceding for 6 h cisplatin infusion, 30 mg/m(2)/24 h cisplatin intravenous (i.v.) bolus days 1-4 and 1000 mg/m(2)/24 h 5-FU in a 4-h infusion on days 1-4. Patients in arm B were given cisplatin and 5-FU in the same dosage and schedule as in arm A. Additional irradiation+/-surgery was performed if and when feasible. Patients in both arms were well balanced with regard to clinical variables. The following results were obtained: Arm A: 84 patients were included, 74 were evaluable for activity; RESPONSE: complete response (CR) 8 (11%), partial response (PR) 40 (54%), stable disease (SD) 11 (15%), progressive disease (PD) 15 (20%). The overall response rate (RR) based on the evaluable patients was 48/74 (65%, 95% confidence interval (CI) 54-75%); The RR based on an intent-to-treat analysis was 57%, 95% CI 47-67%; Median survival was 13 months; There were 50 episodes of granulocytopenia grade IV and 15 of febrile neutropenia per 316 cycles. Arm B: 86 patients were included, 80 were evaluable for activity; RESPONSE: CR 7 (9%), PR 29 (36%), SD 10 (12.5%), PD 34 (42.5%); The overall RR based on the evaluable patients was 36/80 (45%, 95% CI 35-56%); The RR based on an intent-to-treat analysis was 42%, 95% CI 32-52%; Median survival was 8 months; There were 14 episodes of granulocytopenia grade IV and 7 febrile neutropenias per 324 cycles. The RR was significantly higher in arm A (P=0.013), power (one-sided) 80%. The proportion of patients from the appropriate subset who achieved a clinical response making additional treatment feasible was higher in arm A (P=0.00015), as well as the proportion of patients with a performance status 2+3 achieving a response (P<0.0001). Using the Log-rank test, patients from arm A achieved a significantly longer survival (P=0.009), with the probability of survival at 12 months of 0.58 for patients in arm A and 0.28 for patients in arm B. Grade IV granulocytopenia and thrombocytopenia were more frequent in arm A. Due to its haematological side-effects, cytarabine might not be the ideal drug to modulate the cytotoxicity of cisplatin. However, other modulators of its activity could be of interest for further studies in head and neck cancer patients.

Adult↗
PubMed1997

S-phase fractions of breast cancer predict overall and post-relapse survival.

We studied the correlation of S-phase fraction (SPF) with clinical outcome in 127 pre- or perimenopausal patients with breast cancers treated by neoadjuvant chemotherapy from October 1986 to June 1990. When the patients were analysed using the median value of the SPF as a threshold, there was a small but non-significant difference in favour of low SPF tumours for metastasis-free survival. SPF was the only parameter predicting overall survival in multivariate analysis (P < 0.002) which included T, N, histopathological grade and steroid hormone receptors. The results of metastasis-free survival contrasted with previous analyses with shorter follow-up, so we tested the time-dependent influence of SPF on prognosis. It was thus shown that SPF significantly predicts metastasis-free survival only during the first 30 months, whereas the relative risk of cancer-related death according to SPF remains significant for 56 months. In order to find an explanation for the difference in predictivity between metastasis-free survival and overall survival, we studied the post-relapse survival. Significantly shorter survival (median 12 months) was associated with tumours presenting pre-treatment high SPF values, compared to the low SPF group for which 60% of the patients were still alive after 30 months of metastasis phase (P = 0.002). Our current results, in a homogeneous series with a median follow-up of over 5 years, emphasise the importance of proliferation-related parameters for breast cancer management.

Adult↗
PubMed1999

Increased use of prophylactic vena cava filters in trauma patients failed to decrease overall incidence of pulmonary embolism.

BACKGROUND: Recent studies have reported that placement of vena cava filters (VCFs) early after injury may decrease the incidence of pulmonary embolism (PE) in high-risk trauma patients. STUDY DESIGN: This was a retrospective review of all trauma patients with placement of VCFs admitted to a single level-1 trauma center between 1989 and 1997. Two cohorts corresponding to years of high or low prophylactic VCF use (PVCF) were compared. RESULTS: Records were reviewed for 299 trauma patients identified as having had placement of a VCE Two hundred forty-eight filters were placed before the diagnosis of PE. During years of low PVCF use, the overall PE incidence was 0.31%; during years of high PVCF use, the incidence of PE was higher at 0.48% (p = 0.045, chi-square). CONCLUSIONS: Increased use of PVCFs failed to decrease the overall rate of PE in our trauma patient population.

Adult↗
PubMed2002

Characterization of rainbow trout branched-chain alpha-keto acid dehydrogenase complex: inter-domain segments of the E2 component affect the overall activity.

Branched-chain alpha-keto acid dehydrogenase complex (BCKADH) contains decarboxylase (E1), dihydrolipoyl transacylase (E2), and dihydrolipoyl dehydrogenase (E3) as catalytic components. BCKADH purified from rainbow trout (Oncorhynchus mykiss) liver was comparable with mammalian BCKADH in various enzymatic characteristics, but less efficient in catalyzing the overall reaction. The trout E2 subunit was larger than the mammalian subunit and rather similar to the chicken one in relative molecular mass on SDS-PAGE, whereas the E1 component was similar between trout and mammalian both in relative molecular mass of its alpha and beta subunits and in the catalytic activity. Trout E2 cDNA cloning and nucleotide sequencing revealed that the mature trout E2 subunit consists of 435 residues, and possesses 14 additional residues compared with mammalian E2. Eleven of these are localized in two interdomain segments as two sequences with two and nine residues, respectively. Trout E2 was inferior to rat E2 in the capacity for binding the E1 component, similar to chicken E2. Thus, it appears that non-mammalian BCKADH E2 is distinct from that in mammals in the structure of interdomain segments, resulting in reduction of overall activity of the enzyme complex.

Amino Acid Sequence↗
PubMed1997

An automated rotarod method for quantitative drug-free evaluation of overall motor deficits in rat models of parkinsonism.

A variety of tests have been proposed for evaluation of motor deficits in rat models of hemiparkinsonism. The most widely used test, the "rotational behaviour" test, is based upon motor asymmetry induced by drug administration, leading to problems of sensitization, conditioning and priming. In addition, lesion-induced rotational behaviour is sometimes overcompensated by treatments (grafts) while other deficits are unaffected. However, rotational behaviour is reproducible and easy to quantify. On the contrary, most drug-free tests have proved of limited applicability because of subjective scaling, excessive interaction between the experimenter and animals, motivational effects, excessively complex tasks, etc., making it difficult to compare results from different laboratories. In this paper, we present a rotarod based method for automated drug-free evaluation of overall motor deficits in the rat model of hemiparkinsonism, and for identifying treatment-induced changes. Animals are pre-trained on the rotarod and then tested at a series of increasing rod speeds; from this set of values a unique score for each animal is computed (the overall rotarod performance, ORP) summarizing its performance at different speeds. This value is easy to compute and greatly simplifies statistical comparisons. Major advantages of the test are: (i) it does not require drugs, but is nevertheless highly objective, reproducible and easy to quantify; and (ii) falling of animals from rotating rod seems to depend on a combination of lesion-induced deficits which become more evident when rats are forced to move at faster speeds. Since the test is not based exclusively on motor asymmetry, it may also be useful for characterization of bilaterally lesioned animals, for which drug-induced rotational behaviour tests cannot be used.

Animals↗
PubMed1994

13C-NMR relaxation in three DNA oligonucleotide duplexes: model-free analysis of internal and overall motion.

Natural-abundance 13C-NMR spectra of [d(TCGCG)] (1), [d(CGCGCG)]2 (2), and [d(GGTATACC)]2 (3) were measured at 90.6 MHz to obtain 13C-1H NOEs and T1 relaxation times; relaxation data were also measured at 125.7 MHz for 1 and 2 and at 62.9 MHz for 1. Analysis of the relaxation data was performed in the context of the "model-free" approach of Lipari and Szabo [Lipari, G., & Szabo, A. (1982) J. Am. Chem. Soc. 104, 4546-4559], leading to the following conclusions: (i) Optimized values for the overall correlation times of 0.9 ns for 1 and 1.4 ns for 2 are close to those predicted by light-scattering results on similar molecules [Eimer et al. (1990) Biochemistry 29, 799-811]. (ii) For the nonterminal residues, the "order parameter", S2, is around 0.8 for the protonated base carbons and 0.6 for the sugar carbons, indicating less spatial restriction on the sugar carbons (in the model-free approach, the order parameter is 1 for a rigid body and 0 for a system with completely unrestricted internal motion). (iii) The order parameters for the terminal residues vary over a wide range with the smallest values around 0.2-0.3 for the HO-13C5' and the 13C3'-OH; rational trends are seen in the variation of S2 with chain position in the terminal residues. (iv) The analysis shows that the order parameters are accurate within 15%. (v) The "effective internal correlation time", tau e, is very short for the sugar carbons (30-300 ps) and less well-defined, but probably also short, for the bases. (vi) The analysis indicates that most of the relaxation in DNA is accounted for by S2 and the tau e is so short that a good approximation to any relaxation property, P (e.g., T1, T2, 13C-1H NOE, 1H-1H cross-relaxation rate), is P = S2Prigid, where Prigid is the value for the property in a system without internal motion (the analysis assumes the same isotropic overall motion for both the rigid and flexible bodies).

Base Sequence↗
PubMed1996

Formation of the alpha-aminoacrylate immediate limits the overall reaction catalyzed by O-acetylserine sulfhydrylase.

O-Acetylserine sulfhydrylase-A (OASS-A) catalyzes the final step in the synthesis of L-cysteine, viz., the beta-substitution of acetate in O-acetyl-L-serine (OAS) by sulfide via a ping-pong kinetic mechanism . Rapid-scanning stopped-flow and single-wavelength absorbance and fluorescence stopped-flow experiments were carried out to obtain information on the location and amount of limitation of rate-determining steps for the overall reaction and the individual half-reactions of OASS-A. The first half-reaction, conversion of OAS to the alpha-aminoacrylate intermediate and acetate, is rate-limiting for the overall reaction catalyzed by OASS-A. No intermeidates are detected within the second half-reaction, and thus rate constants for all steps must be > or = 1000s-1 at the lowest sulfide concentration used. Within the first half reaction, formation of the extrernal Schiff base (Kassociation = 0.2 mM-1) is observed in the first milliseconds, followed by its slower conversion to the alpha-aminocacrylate intermediate with a rate constant of 300 s-1, close to the value of 130 s-1 obtained for V/Et [Tai, C.H., Nalabolu, S.R., Jacobson, T.M., Minter D.E., & Cook, P.F. (1993) Biochemistry 32, 6433-6442]. Addition of L-cysterine ot OASS-A results in a rapid formation of the external Schiff base (Kassociation = 6.7 mM-1), followed by transient formation of the alpha-aminoacylate intermediate with a slightly lower rate (70-100 s-1) compared to OAS. The alpha-aminoacrylate intermediate decays to generate a species absorbing maximally at 418 nm, resulting from attack of the cysteine thiol to give ether in external Schiff base linkage with the active site PLP.

Alanine↗
PubMed2006

Quantification of DNA BI/BII backbone states in solution. Implications for DNA overall structure and recognition.

The backbone states of B-DNA influence its helical parameters, groove dimensions, and overall curvature. Therefore, detection and fine characterization of these conformational states are desirable. Using routine NMR experiments on a nonlabeled B-DNA oligomer and analyzing high-resolution X-ray structures, we investigated the relationship between interproton distances and backbone conformational states. The three H2'i-H6/8i+1, H2' 'i-H6/8i+1, and H6/8i-H6/8i+1 sequential distances were found cross-correlated and linearly coupled to epsilon-zeta values in X-ray structures and 31P chemical shifts (deltaP) in NMR that reflect the interconversion between the backbone BI (epsilon-zeta < 0 degrees ) and BII (epsilon-zeta > 0 degrees) states. These relationships provide a detailed check of the NMR data consistency and the possibility to extend the set of restraints for structural refinement through various extrapolations. Furthermore, they allow translation of deltaP in terms of BI/BII ratios. Also, comparison of many published deltaP in solution to crystal data shows that the impact of sequence on the BI/BII propensities is similar in both environments and is therefore an intrinsic and general property of B-DNA. This quantification of the populations of BI and BII is of general interest because these sequence-dependent backbone states act on DNA overall structure, a key feature for DNA-protein-specific recognition.

DNA↗
PubMed2003

Influence of different oligosaccharides and inulin on heterocyclic aromatic amine formation and overall mutagenicity in fried ground beef patties.

The effects of different oligosaccharides [fructooligosaccharide (FOS), galactooligosaccharide (GOS), and isomaltooligosaccharide (MOS)] and inulin on heterocyclic aromatic amine (HAA) formation and overall mutagenicity in fried ground patties were evaluated. Different oligosaccharides and inulin was added directly to ground beef. Patties (100 g) were fried at 225 degrees C (surface temperature) for 10 min per side. FOS added at levels of 0.5, 1.0, 1.5, 2.0, and 2.5 g to 100 g of ground beef inhibited total HAA formation by 19, 32, 45, 51, and 58%, respectively. The addition of 1.5 g of FOS, GOS, MOS, and inulin to ground beef patties inhibited total HAA formation by 50, 47, 46, and 54%, respectively. They also reduced overall mutagenicity by 52, 51, 48, and 59%, respectively. These studies confirm that oligosaccharides and inulin have the potential to reduce HAA formation in cooked beef patties.

Amines↗
PubMed2006

Efficient overall water splitting under visible-light irradiation on (Ga(1-x)Zn(x))(N(1-x)O(x)) dispersed with Rh-Cr mixed-oxide nanoparticles: Effect of reaction conditions on photocatalytic activity.

The photocatalytic activity of (Ga(1-x)Zn(x))(N(1-x)O(x)) loaded with Rh-Cr mixed-oxide (Rh(2-y)Cr(y)O3) nanoparticles for overall water splitting under visible-light irradiation (lambda > 400 nm) is investigated with respect to reaction pH and gas pressure. The photocatalytic performance of the catalyst is found to be strongly dependent on the pH of the reactant solution but largely independent of gas pressure. The present photocatalyst exhibits stable and high photocatalytic activity in an aqueous solution of pH 4.5 for 72 h. The photocatalytic performance is much lower at pH 3.0 and pH 6.2, attributable to corrosion of the cocatalyst and hydrolysis of the catalyst. The dispersion of Rh(2-y)Cr(y)O3 as a cocatalyst on the (Ga(1-x)Zn(x))(N(1-x)O(x)) surface promotes hydrogen evolution, which is considered to be the rate-determining step for overall water splitting on this catalyst.

Journal Article↗
PubMed2006

Effect of high-pressure ammonia treatment on the activity of Ge3N4 photocatalyst for overall water splitting.

The photocatalytic activity of beta-Ge(3)N(4) powder for overall water splitting is successfully enhanced by ammonia treatment at 823 K for 5-24 h at ammonia pressures of 20 MPa or greater. The surface and bulk nitrogen content in the treated samples varies according to the treatment temperature and treatment time, related to the stability of beta-Ge(3)N(4) powder under pressurized ammonia. The change in nitrogen content resulted in a change in the photocatalytic activity for overall water splitting. A beta-Ge(3)N(4) powder treated at 823 K for 5 h under ammonia at 20 MPa exhibited a photocatalytic activity 4 times higher than that of the as-synthesized powder, attributable to a decrease in the density of anion defects in the bulk and surface.

Journal Article↗
PubMed2001

Nodulisporic acid A synthetic studies. 1. Overall strategy and construction of a western hemisphere subtarget.

In this, the first of two Letters, we outline our overall strategy for the construction of (+)-nodulisporic acid A (1), a representative member of a new class of indole diterpenes. In addition, we describe the efficient assembly of (-)-6, an advanced western hemisphere subtarget, comprising the ABC rings of (+)-nodulisporic acid A (1). The synthesis proceeded in 9% overall yield (longest linear sequence, 11 steps), exploiting a Shibasaki-Mori tandem transmetalation-cyclization to construct ring B. [reaction: see text]

Indoles↗
PubMed1998

Internal and overall motions of the translation factor eIF4E: cap binding and insertion in a CHAPS detergent micelle.

The mRNA cap-binding protein eIF4E is the limiting factor in the eIF4F translation initiation complex, which mediates the binding of the 40S ribosome to the mRNA. 15N relaxation studies have been used to characterize the backbone dynamics of deuterated eIF4E in a CHAPS micelle for the apoprotein, the m7GDP-bound form, and the dinucleotide (m7GpppA)-bound form, as well as for CHAPS-free eIF4E. Large differences in overall correlation time between the CHAPS-free form (11.8 ns) and samples containing different concentrations of CHAPS (15.9-19.4 ns) indicate that eIF4E is embedded in a large micelle in the presence of CHAPS, with a total molecular weight in the range of 40-60 kDa. CHAPS seems to restrict the mobility of the a2-b3 and a4-b5 loops which are thought to be embedded in the micelle. No significant changes in overall mobility were seen between the m7 GDP-bound form, the m7GpppA-bound form, and the apoprotein. Amide hydrogen exchange data indicate the presence of slowly exchanging amides in two surface-exposed helices (a2 and a4), as well as the a4-b5 loop, indicating protection by the CHAPS micelle. The micelle covers the convex side of the protein away from the cap-binding site.

Cholic Acids↗