bluuebunny/crossref_metadata_2025 huggingface dataset:
Formulae for cause‐deleted life tables
Authors: Smith David P.
Published: April 2007

The medical and demographic literature contain two popular formulae for the construction of cause‐deleted life table lx values, one developed for applications in follow‐up studies and the other for cross‐sectional studies. It turns out that for both types of applications one of the two formulae is virtually always of better quality than the other. A formula developed by Keyfitz and Frauenthal5 is usually better than either.
Comparison of ascertainment‐bias correction schemes for pedigrees ascertained through multiple probands
Authors: Majumder Partha P.
Published: April 2007

Assessing the genetic causation of a disease, which is of prime importance in medical genetics, is usually done by analysing pedigree data. When gathering such data, it is often more practical to adopt a non‐random sampling strategy. However, unless suitable corrections for non‐random sampling are made at the time of data analysis, inferences may be grossly affected. For pedigree data ascertained through multiple probands, various correction schemes have been suggested, although the efficiencies of these schemes are unknown. This paper compares such schemes, using Monte Carlo simulation techniques, under a simple genetic model, for pedigrees of fixed sizes and structures and for probands of two types of relationship‐parent‐offspring, and a pair of siblings. It is found that gene frequencies are grossly overestimated and the penetrance value of heterozygotes slightly underestimated whether or not any correction for non‐random sampling of pedigrees is made. Knowledge of the population value of the gene frequency improves the estimate of the penetrance parameter.
Comparative analysis of two rates
Authors: Miettinen Olli , Nurminen Markku
Published: April 2007

In this paper, we examine comparative analysis of rates with a view to each of the usual comparative parameters‐rate difference (RD), rate ratio (RR) and odds ratio (OR)‐and with particular reference to first principles. For RD and RR we show the prevailing statistical practices to be rather poor. We stress the need for restricted estimation of variance in the chi‐square function underlying interval estimation (and also point estimation and hypothesis testing). For RR analysis we propose a chi‐square formulation analogous to that for RD and, thus, one which obviates the present practice of log transformation and its associated use of Taylor series approximation of the variance. As for OR analysis, we emphasize that the chi‐square function, introduced by Cornfield for unstratified data, and extended by Gart to the case of stratified analysis, is based on the efficient score and thus embodies its optimality properties. We provide simulation results to evince the better performance of the proposed (parameter‐constrained) procedures over the traditional ones.
Assessing apparent treatment—covariate interactions in randomized clinical trials
Authors: Byar David P.
Published: April 2007

In the context of clinical trials, a qualitative treatment—covariate interaction occurs when a patient's preferred treatment depends on his covariates. In this paper I review the nature and interpretation of various kinds of interactions, compare the use of overall tests for interaction to subset analysis, present some examples of apparent treatment‐covariate interactions that have arisen in actual randomized clinical trials, and discuss some recent work by others related to significance testing, estimation and assessment of apparent treatment—covariate interactions.
Prognostic factors for stagei melanoma of the skin: A review
Authors: Cascinelli N. , Marubini E. , Morabito A. , Bufalino R.
Published: April 2007

The prognosis of melanoma of the skin has been investigated in many studies. In this report papers on the prognosis of stage I melanoma published since 1975 in the leading oncology journals have been reviewed. Further the data collected by the WHO Collaborating Centre for Evaluation of Methods of Diagnosis and Treatment of Melanoma are analysed, and the results compared with those of other series. Three factors emerge as clearly influencing prognosis: sex, maximum tumour thickness and ulceration. The role of other factors and particularly that of an interaction between tumour thickness and ulceration conjectured by some authors remains questionable.
Critical discussion of the assessment of a three‐stage prognostic classification for chronic lymphocytic leukemia
Authors: Chastang Claude , Travade Philippe , Auquier Ariane
Published: April 2007

A study of the prognosis of two series of chronic lymphocytic leukemia (CLL) patients (99 from a retrospective series and 196 from a prospective series) has led us to propose a three‐stage classification (A, B, C), requiring only a clinical examination and a haemogram.

For stage A patients (comprising 50% of the CLL patients), survival rates are similar to those in the French general population of the same age and sex; median survival time is six years for stage B patients (comprising 35% of CLL) and two years for stage C patients (comprising 15%).

Several methodological difficulties were encountered with the data and the statistical strategy, and these are discussed. The staging system has been justified, since the results have now been confirmed in four other series, totalling 611 CLL patients.
Comparison of the mortality of a cohort with the mortality of a reference population in a prognostic study
Authors: Hill Catherine , Laplanche Agnes , Rezvani Ali
Published: April 2007

It is standard practice in epidemiological studies to compare the observed mortality of a cohort to the mortality expected in a reference population of the same age and sex distributions computed from national statistics. The same methods can be used in a prognostic study where the effects on survival of potential prognostic factors are studied in a cohort of patients with a given disease. Writing the hazard function in the cohort as the product of the hazard function in the reference population and a function of some characteristics of the patients, one can derive simple estimates and statistical tests of the standardised mortality ratios (Breslow et al.1). The study of a cohort of patients with thyroid cancer will provide an example.
Computer assistance for C.T. scan interpretation and cerebral disease diagnosis
Authors: Teather D. , Morton B. A. , du Boulay G. H. , Wills K. M. , Plummer D. , Innocent P. R.
Published: April 2007

This paper describes the development and use of a system to aid in the radiological interpretation of C.T. scan images of patients with cerebral disease. The system is able to provide guidance, both on diagnosis and the need for further scan investigations. Explanation and help facilities, similar to those found in certain rulebased expert systems, are available on demand. Diagnostic and other advice is, however, based on hard statistical data. The scan interpretation and diagnostic system offers important benefits in the training of less experienced radiologists.
Knowledge based expert systems for medical diagnosis
Authors: Torasso Pietro
Published: April 2007

‘Knowledge based expert systems’ have been developed in the last decade for many different applications by adopting artificial intelligence techniques. The paper discusses the main characteristics of the expert systems devoted to medical diagnosis (knowledge representation, explanation capability, inexact reasoning) and addresses some of the limitations (mainly system validation and knowledge acquisition). Finally the paper sketches the overall organization of an expert system devoted to the evaluation of liver function.
Latent class analysis in chronic disease epidemiology
Authors: Kaldor John , Clayton David
Published: April 2007

Latent class analysis provides a useful framework for the analysis of epidemiological data which may have been mismeasured. In this paper, the latent class model is described in the context of logistic regression with categorical variables, and some examples of its application are provided. In particular, it is shown that adjustment for a misclassified confounding variable can be greatly improved by using the methods presented.
Hypothesis testing in the polychotomous logistic model with an application to detecting gastrointestinal cancer
Authors: Marshall R. J. , Chisholm E. M.
Published: April 2007

We discuss the use of the trichotomous logistic model to discriminate between patients with gastrointestinal(GI) cancer, patients with benign GI disease and ‘normal’ subjects, using symptoms and the concentrations of some serum proteins that are potentially indicative of malignancy as covariates. A parsimonious model can be obtained by invoking an indistinguishability hypothesis which is appropriate when a covariate is considered to have no predictive value between categories. It is shown that the polychotomous model can be re‐parameterised under the null hypothesis to give a ‘reduced form’, which can be fitted by maximum likelihood. The validity of the use of the same methods for retrospective sampling is discussed. The approach is illustrated by the development of a logistic model to identify symptomatic and asymptomatic subjects with a high risk of GI cancer.
Assessment of some risk factors for hepatocellular carcinoma: A case control study
Authors: Filippazzo M. G. , Aragona E. , Cottone M. , Dardanoni G. , Lanzarone F. , Marenghini A. , Patti C. , Sciarrino E. , Simonetti R. , Tine F. , Pagliaro L.
Published: April 2007

A case‐control study of risk for hepatocellular carcinoma (HCC) was carried out in our Department from December 1980 to December 1983. One hundred and twenty consecutive inpatients with HCC were compared with 360 controls pair‐matched by sex and age (within years). For each case three different controls were selected from inpatients at the same hospital: one patient with liver cirrhosis; one patient with solid tumor and one patient with chronic illness other than neoplasm or liver disease. We report here the results on alcohol consumption, smoking habit and hepatitis B virus infection. The risk factors investigated are distributed similarly in HCC and cirrhosis. The prevalence of alcohol abuse in HCC is similar to that in cirrhosis and is significantly higher than in other neoplastic or otherwise chronically ill patients (odds ratio 2.3 and 3.2 respectively). Thus alcohol abuse is probably a risk factor for HCC as a cause of cirrhosis.

Smoking habits were similar among the various disease groups and independent of alcohol consumption. The prevalence of heavy smoking was comparable in cases and controls. HbsAg negative‐HCC with an ultrasonographic pattern of ‘diffuse’ alteration was more frequent in heavy smokers.
Comparison of three devices for measuring blood pressure
Authors: Bassein Leona , Borghi Claudio , Costa Francesco Vittorio , Strocchi Enrico , Mussi Alessandra , Ambrosioni Ettore
Published: April 2007

Blood pressure measurement with two automatic devices, Dinamap 845 and Sentry, was compared with the standard mercury sphygmomanometer, by means of a 3‐period crossover experiment. Both automatic devices read diastolic pressure considerably lower than the mercury sphygmomanometer (about 7 mmHg on average); agreement was better for systolic pressure. Device differences in individual patients were often much higher. To assess the patient's emotional pressor response during manual measurement, Dinamap was used to monitor blood pressure before, during and after measurement with the mercury sphygmomanometer. No rise in pressure was found. It is concluded that the three devices can often give different values, and that the physician's involvement cannot explain these differences.
Are routine clinical chemistry analyses ‘in control’ according to shewhart's technique?
Authors: Boerma G. J. M.
Published: April 2007

The clinical laboratory routinely uses quality control (QC) procedures. The Shewhart technique of charting control data, introduced in 1950, is usually applied in a much simplified manner. This reduces its power to distinguish between random errors and errors due to assignable causes. In a comparison of one of our routine charting procedures with a correct Shewhart procedure we checked 23 chemical tests. We found that using the latter ‘a stable system of chance causes’ did not exist for 6 tests. Both control procedures agreed well on the evaluation of reproducibility. For three of the tests, albumin, urea and uric acid, the instability was not detected by the routine procedure.

Although charting of group means (x̄i) and ranges (Ri) more readily detected instability, it did not lead to a negation of the practical utility of our patient data.
The pattern of ischemic heart disease 1931–1980
Authors: Smith David P. , Slater Carl
Published: April 2007

The rise in ischemic heart disease in the U.S. after 1920 has been described in the literature both as a 20th century epidemic and as an artifact of the decline of competing causes of death, particularly the infectious, parasitic and diarrheal diseases. Shifting medical terminology and occasional major revisions in cause of death codes have aggravated efforts to resolve the debate. Through regression analysis and ordinary and cause‐deleted life tables we trace the course of the disease. The accumulated evidence points to a major epidemic but one largely confined to males. Reversals in patterns are now beginning.
Selecting risk factors: A comparison of discriminant analysis, logistic regression and cox's regression model using data from the tromsø heart study
Authors: Brenn Tormod , Arnesen Egil
Published: April 2007

For comparative evaluation, discriminant analysis, logistic regression and Cox's model were used to select risk factors for total and coronary deaths among 6595 men aged 20–49 followed for 9 years. Groups with mortality between 5 and 93 per 1000 were considered. Discriminant analysis selected variable sets only marginally different from the logistic and Cox methods which always selected the same sets. A time‐saving option, offered for both the logistic and Cox selection, showed no advantage compared with discriminant analysis. Analysing more than 3800 subjects, the logistic and Cox methods consumed, respectively, 80 and 10 times more computer time than discriminant analysis. When including the same set of variables in non‐stepwise analyses, all methods estimated coefficients that in most cases were almost identical. In conclusion, discriminant analysis is advocated for preliminary or stepwise analysis, otherwise Cox's method should be used.
Assessing the adequacy of the logistic regression model for matched case‐control studies
Authors: Moolgavkar Suresh H. , Lustbader Edward D. , Venzon David J.
Published: April 2007

We apply results for the detection of outliers in logistic regression to the analysis of matched pairs data and illustrate the techniques with data from a matched pairs study of the relationship between iron‐binding proteins and mortality in the Solomon Islands. Although the study includes 90 matched pairs, the conclusions change substantially with deletion of one or two pairs. Thus, even with reasonably large data sets, single observations may have a great impact on the results of an analysis. The identification of influential observations should constitute part of the analysis of matched case‐control data.
Using test‐retest reliability data to improve estimates of relative risk: An application of latent class analysis
Authors: Clayton David
Published: April 2007

The paper discusses the problem of interval estimation for the relative risk when some test‐retest data are available on random subsamples drawn from case‐control studies. It is shown that, although the upper portion of the interval may be very wide indeed, the lower bound of the interval estimate may be improved considerably by the collection of even modest amounts of repeat measurements.
The cusum test of homogeneity with an application in spontaneous abortion epidemiology
Authors: Levin Bruce , Kline Jennie
Published: April 2007

We test the hypothesis of homogeneity over time in the rate of an event with a modification of Page's cumulative sum (cusum) procedure. The modification draws on an indifference zone approach to testing that is well suited to the epidemiologic study of retrospective data. We provide procedures for evaluating the significance level of the largest observed cusum value occurring in a sequence of fixed length. We draw inferences unconditionally with a known baseline rate of the event, and conditionally on observed margins with unknown baseline rate. Data collected over a five year period from one New York City hospital serve to illustrate the modified cusum test in a study of fluctuations in the proportions of chromosomally normal, trisomic, X‐monosomic and triploid spontaneous abortions.
The value of specialized tests in studies where ordered group means are expected
Authors: Shirley Eryl A. C.
Published: April 2007

The performances of three tests for ordered means (Bartholomew's, Williams' and a modified method of least significant differences) are compared with the performances of more general multiple comparison procedures. The tests are assessed using simulated data representing various patterns of results from a toxicological study with one (zero dose) control group and three treatment groups. The specialized tests are considerably more powerful than the general tests and their application is recommended whenever ordered group means are expected.
Optimal designs for clinical trials with dichotomous responses
Authors: Berry Donald A. , Pearson Larry M.
Published: April 2007

We consider two‐stage designs for clinical trials that involve two treatments with dichotomous responses. The first is the information‐gathering stage; the treatment chosen as the better from first stage and prior data is used exclusively in the second stage. Determination of treatment allocation in the first stage results from weighing the anticipated gain in information with effective treatment; the objective is to maximize the expected number of successes in the entire trial. This is in contrast to randomized controlled trials with the restricted objective of obtaining information concerning treatment differences. We allow the length of the first stage to be arbitrary and fixed in advance, or optimized as a function of prior information and the ‘patient horizon’. We can regard this patient horizon as either the number of patients in the trial or the number who have the condition under treatment. We consider two forms of prior information: (i) both success probabilities known but the better of the two treatments is unknown, and (ii) one success probability known whereas the other has an arbitrary distribution. In many instances of the latter case the optimal first stage size is of the order of the square root of the patient horizon.
An application of bayesian analysis to medical follow‐up data
Authors: Achcar Jorge A. , Brookmeyer Ron , Hunter William G.
Published: April 2007

Posterior distributions can provide effective summaries of the main conclusions of medical follow‐up studies. In this article, we use Bayesian methods for the analysis of survival data. We describe posterior distributions for various parameters of clinical interest in the presence of arbitrary right censorship. Non‐informative reference priors result from transformation of a two‐parameter Weibull model into a location‐scale family. We suggest an approach for checking adequacy. For illustration, we apply the methods to a well‐known acute leukemia data set.
Analysis of the clinical utility of a predictive chemosensitivity assay
Authors: Korn Edward L. , Sondak Vernon K. , Bertelsen Carl A. , Kern David H.
Published: April 2007

We present an elementary statistical analysis for quantifying the clinical utility of a predictive chemosensitivity assay based on retrospective data. An assay predictive of patient response could possibly improve response rates and reduce morbidity by individualizing chemotherapy for each patient. An analysis of retrospective data can suggest appropriate patient populations and sample sizes for study in prospective trials using the chemosensitivity assay. We provide an example with data from a clonogenic assay collected on melanoma patients.
A predictive approach to selecting the size of a clinical trial, based on subjective clinical opinion
Authors: Spiegelhalter D. J. , Freedman L. S.
Published: April 2007

The ‘textbook’ approach to determining sample size in a clinical trial has some fundamental weaknesses which we discuss. We describe a new predictive method which takes account of prior clinical opinion about the treatment difference. The method adopts the point of clinical equivalence (determined by interviewing the clinical participants) as the null hypothesis. Decision rules at the end of the study are based on whether the interval estimate of the treatment difference (classical or Bayesian) includes the null hypothesis. The prior distribution is used to predict the probabilities of making the decisions to use one or other treatment or to reserve final judgement. It is recommended that sample size be chosen to control the predicted probability of the last of these decisions. An example is given from a multi‐centre trial of superficial bladder cancer.
Influence of Different ECM Mimetic Peptide Sequences Embedded in a Nonfouling Environment on the Specific Adhesion of Human‐Skin Keratinocytes and Fibroblasts on Deformable Substrates
Authors: Salber Jochen , Gräter Stefan , Harwardt Marc , Hofmann Matthias , Klee Doris , Dujic Jadranka , Jinghuan Huang , Ding Jiandong , Kippenberger Stefan , Bernd August , Groll Jürgen , Spatz Joachim P. , Möller Martin
Published: April 2007

Mechanical stress is a decisive factor for the differentiation, proliferation, and general behavior of cells. However, the specific signaling of mechanotransduction is not fully understood. One basic problem is the clear distinction between the different extracellular matrix (ECM) constituents that participate in cellular adhesion and their corresponding signaling pathways. Here, a system is proposed that enables mechanical stimulation of human‐skin‐derived keratinocytes and human dermal fibroblasts that specifically interact with peptide sequences immobilized on a non‐interacting but deformable substrate. The peptide sequences mimic fibronectin, laminin, and collagen type IV, three major components of the ECM. To achieve this, PDMS is activated using ammonia plasma and coated with star‐shaped isocyanate‐terminated poly(ethylene glycol)‐based prepolymers, which results in a functional coating that prevents unspecific cell adhesion. Specific cell adhesion is achieved by functionalization of the layers with the peptide sequences in different combinations. Moreover, a method that enables the decoration of deformable substrates with cell‐adhesion peptides in extremely defined nanostructures is presented. The distance and clustering of cell adhesion molecules below 100 nm has been demonstrated to be of utmost importance for cell adhesion. Thus we present a new toolbox that allows for the detailed analysis of the adhesion of human‐skin‐derived cells on structurally and biochemically decorated deformable substrates.
Kinetic evaluation in nonhuman primates of two new PET ligands for peripheral benzodiazepine receptors in brain
Authors: Imaizumi Masao , Briard Emmanuelle , Zoghbi Sami S. , Gourley Jonathan P. , Hong Jinsoo , Musachio John L. , Gladding Robert , Pike Victor W. , Innis Robert B. , Fujita Masahiro
Published: April 2007

Peripheral benzodiazepine receptors (PBRs) are upregulated on activated microglia and are, thereby, biomarkers of cellular inflammation in brain. We recently developed two PET ligands with an aryloxyanilide structure to image PBRs and now evaluate the kinetics of these radiotracers in monkey to determine whether they are suitable to explore in human. Baseline and receptor‐blocking scans were performed with [11C]PBR01 and [18F]PBR06 in conjunction with serial measurements of the arterial plasma concentration of parent radiotracer separated from radiometabolite. We used brain and plasma data with compartmental modeling to calculate regional brain distribution volume, which is equal to the ratio at equilibrium of the concentration of radioligand in brain to that of plasma. The distribution volume of [11C]PBR01 was inaccurately estimated in the baseline scans, possibly because of the short half‐life of 11C or the presence of radiometabolite in brain. In contrast, the distribution volume of [18F]PBR06 was stably determined within 200 min of scanning, and nondisplaceable uptake was only ∼10% of total brain uptake. [18F]PBR06 is promising for use in human because brain activity could be quantified with standard compartmental models and showed higher ratios (∼10:1) of specific to nonspecific uptake. A critical factor for human use will be whether the tracer has adequately fast wash out from brain relative to the half‐life of the radionuclide to obtain stable values of distribution volume. Synapse 61:595–605, 2007. Published 2007 Wiley‐Liss, Inc.
In vitro and in vivo characterization of [3H]CNS‐5161—A use‐dependent ligand for the N‐methyl‐d‐aspartate receptor in rat brain
Authors: Biegon Anat , Gibbs Andrew , Alvarado Maritza , Ono Michele , Taylor Scott
Published: April 2007

Glutamate is the major excitatory neurotransmitter in the brain. Glutamate activation of the N‐methyl‐d‐aspartate (NMDA) receptor subtype is thought to mediate important physiological and pathological processes, including memory formation and excitotoxicity. The goal of the present work was to characterize and validate a candidate agent for noninvasive positron emission tomography (PET) imaging of this receptor. [3H]‐labeled N‐[3‐3H]‐methyl‐3‐(thiomethylphenyl)cyanamide (CNS‐5161) was incubated with rat brain homogenates at increasing concentrations, temperatures, and times to establish the binding kinetics and affinity of the ligand in vitro. Nonspecific binding was measured with 100 μM MK‐801. The compound was also injected i.v. in rats pretreated with saline, NMDA, MK801, or a combination, and organ and brain regional uptake was assessed at various times after injection by autoradiography or dissection. Blood and brain samples were assayed for metabolites by high‐performance liquid chromatography. CNS‐5161 binds brain membranes with high affinity (Kd < 4 nM) and fast association and dissociation kinetics. Specific binding increased in the presence of glutamate and glycine. Intravenous administration in control rats resulted in a heterogeneous brain distribution with hippocampus and cortex ≫ thalamus ≫ striatum ≫ cerebellum, and a cortex/cerebellum ratio of 1.4. Pretreatment with NMDA increased the hippocampus‐to‐cerebellum ratio to 1.6–1.9 while MK801 abolished this increase, resulting in ratios close to 1. Thus, CNS‐5161 binds preferentially to the activated state of the NMDA receptor channel in vitro and in vivo. The high affinity and fast kinetics make it compatible with PET imaging of a carbon‐11 labeled CNS‐5161. Synapse 61:577–586, 2007. Published 2007 Wiley‐Liss, Inc.
Cocaine induces the expression of homer 1b/c, homer 3a/b, and hsp 27 proteins in rat cerebellum
Authors: Dietrich Jean‐Bernard , Arpin‐Bott Marie‐Pierre , Kao Dany , Dirrig‐Grosch Sylvie , Aunis Dominique , Zwiller Jean
Published: April 2007

The long homer proteins 1b/c, 2a/b, and 3a/b play an important role in postsynaptic neurons by clustering glutamate receptors and by coupling the receptors with various intracellular effectors. Using immunohistochemistry and Western‐blot analysis, this study shows that the expression of the long homer isoforms 1b/c and 3a/b was induced in rat cerebellum in response to cocaine administration. Acute treatment produced a very robust induction of both constitutive isoforms, whereas repeated treatment for 10 days induced a large expression of homer 1b/c and a more modest increase in the expression of the 3a/b isoform. The heat shock protein hsp 27 was also considerably induced in the cerebellum of cocaine‐treated rats, suggesting that it participates in assisting the correct folding of proteins, and by counteracting oxidative stress mechanisms triggered by the psychostimulant. In addition of being expressed in Purkinje neurons, homer 3a/b and hsp 27, but not homer 1b/c, were localized within Bergmann glial cells and in their extensions, which surround Purkinje cells, as assessed by coimmunoreactivity with glial fibrillary acidic protein. Cocaine was also found to induce both proteins in the Bergmann glial cells. Since we found that homer 3a/b colocalized with the mGluR1 receptor in Purkinje cells, the data suggest that the long homer isoforms are involved in the cocaine‐induced neuroplasticity that takes place in the cerebellum, by reshaping postsynaptic densities in Purkinje cell dendrites. Synapse 61:587–594, 2007. © 2007 Wiley‐Liss, Inc.
Clonal propagation in cashew (Anacardium occidentale): effect of rooting media on the rootability and sprouting of air‐layers
Authors: Aliyu OM
Published: April 2007

An evaluation of three different rooting media (topsoil, sawdust and river sand) mixed in different proportions for the rooting of cashew layers was carried out at the Cocoa Research Institute of Nigeria at Ibadan, southwestern Nigeria. Data were collected on percentage take, number of days to rooting, number of roots, root length and percentage sprouting, and were statistically analysed. Significant differences were recorded for the effects of medium, mixture proportion, genotype and medium × mixture proportion interaction, showing the strong influence of the rooting medium (and thus its composition – texture, nutrient status and water‐holding capacity) and the variation in genotypic response to rooting in cashew layers. Topsoil ranked best among the three media tested, and its combination with either sawdust or river sand in the ratio 1 : 1 (v/v) gave the best rooting and sprouting, thus suggesting its use as an effective rooting medium for cashew layering. Copyright © 2007 John Wiley & Sons, Ltd
The structure and function of Saccharomyces cerevisiae proteinase A
Authors: Parr Charity L. , Keates Robert A. B. , Bryksa Brian C. , Ogawa Masahiro , Yada Rickey Y.
Published: April 2007

Saccharomyces cerevisiae proteinase A (saccharopepsin; EC 3.4.23.25) is a member of the aspartic proteinase superfamily (InterPro IPR001969), which are proteolytic enzymes distributed among a variety of organisms. Targeted to the vacuole as a zymogen, its activation at acidic pH can occur by two different pathways, a one‐step process to release mature proteinase A, involving the intervention of proteinase B, or a step‐wise pathway via the autoactivation product known as pseudo‐proteinase A. Once active, S. cerevisiae proteinase A is essential to the activities of other yeast vacuolar hydrolases, including proteinase B and carboxypeptidase Y. The mature enzyme is bilobal, with each lobe providing one of the two catalytically essential aspartic acid residues in the active site. The crystal structure of free proteinase A reveals that the flap loop assumes an atypical position, pointing directly into the S1 pocket of the enzyme. With regard to hydrolysis, proteinase A has a preference for hydrophobic residues with Phe, Leu or Glu at the P1 position and Phe, Ile, Leu or Ala at P1′, and is inhibited by IA3, a natural and highly specific inhibitor produced by S. cerevisiae. This review is the first comprehensive review of S. cerevisiae PrA. Copyright © 2007 John Wiley & Sons, Ltd.
New Series of Porous Ionic Crystals Constructed from Various Polyoxometalate Anions and Macrocations: Syntheses, Crystal Structures, and Comparison with Diverse Spatial Arrangement
Authors: Qu Xiaoshu , Xu Lin , Qiu Yunfeng , Gao Guanggang , Li Fengyan , Yang Yanyan
Published: April 2007

A new series of ionic crystals, KH2[Cr3O(OOCCH3)6(H2O)3][α‐SiMo12O40] · 11 H2O (1), KH2[Cr3O(OOCCH3)6(H2O)3][α‐SiW12O40]μ·μ11H2O (2), K2[Cr3O(OOCCH3)6 (H2O)3][α‐PW12O40]μ· 17H2O (3), Na[Cr3O(OOCCH3)6(H2O)3]2[α‐PMo12O40] · 11H2O (4), H5[Cr3O(OOCCH3)6(H2O)3] [α‐P2Mo18O62] · 10H2O (5) based on a polyoxometalate building block with a macrocation, have been synthesized in aqueous solution and structurally characterized by single‐crystal X‐ray diffraction, IR spectra, elemental analysis, thermogravimetric analysis (TGA). The polyanions and macrocations stacked alternately through hydrogen bonds as well as electrostatic interactions to constitute a novel porous microstructure. In the crystal structures of 1, 2, and 3, oppositely charged cluster ions stacked alternately to form one‐dimensional channels. Compound 4 exhibits an unique structure that six macrocation pillars packed along the a‐axis to form a straight 1D channel, in which accommodates a polyoxometalate pillar. In compound 5, six α‐Dawson‐type polyoxometalate pillars stacked on top of each other along the a‐axis to form a straight 1D channel, which houses a macrocation pillar. The magnetic investigation on compounds 1 and 5 shows a typical antiferromagnetic interaction of the macrocation [Cr3O(OOCCH3)6(H2O)3]+, almost independent from the presence of polyoxometalate anions.
New Hexachalcogeno–Hypodiphosphates of the Alkali Metals: Synthesis, Crystal Structure and Vibrational Spectra of the Hexathiodiphosphate(IV) Hydrates K4[P2S6] · 4 H2O, Rb4[P2S6] · 6 H2O, and Cs4[P2S6] · 6 H2O
Authors: Gjikaj Mimoza , Ehrhardt Claus
Published: April 2007

The new hexathiodiphosphate(IV) hydrates K4[P2S6] · 4 H2O (1), Rb4[P2S6] · 6 H2O (2), and Cs4[P2S6] · 6 H2O (3) were synthesized by soft chemistry reactions from aqueous solutions of Na4[P2S6] · 6 H2O and the corresponding heavy alkali‐metal hydroxides. Their crystal structures were determined by single crystal X‐ray diffraction. K4[P2S6] · 4 H2O (1) crystallizes in the monoclinic space group P 21/n with a = 803.7(1), b = 1129.2(1), c = 896.6(1) pm, β = 94.09(1)°, Z = 2. Rb4[P2S6] · 6 H2O (2) crystallizes in the monoclinic space group P 21/c with a = 909.4(2), b = 1276.6(2), c = 914.9(2) pm, β = 114.34(2)°, Z = 2. Cs4[P2S6] · 6 H2O (3) crystallizes in the triclinic space group $P {\bar 1}$ with a = 742.9(2), b = 929.8(2), c = 936.8(2) pm, α = 95.65(2), β = 112.87(2), γ = 112.77(2)°, Z = 1. The structures are built up by discrete [P2S6]4− anions in staggered conformation, the corresponding alkali‐metal cations and water molecules. O ··· S and O ··· O hydrogen bonds between the [P2S6]4− anions and the water molecules consolidate the structures into a three‐dimensional network. The different water‐content compositions result by the corresponding alkali‐metal coordination polyhedra and by the prefered number of water molecules in their coordination sphere, respectively. The FT‐Raman and FT‐IR/FIR spectra of the title compounds have been recorded and interpreted, especially with respect to the [P2S6]4− group. The thermogravimetric analysis showed that K4[P2S6] · 4 H2O converted to K4[P2S6] as it was heated at 100 °C.
(HgBr2)3(As4S4)2: An Adduct of HgBr2 Molecules and Undistorted As4S4 Cages
Authors: Bräu Michael F. , Pfitzner Arno
Published: April 2007

(HgBr2)3(As4S4)2 is obtained by high temperature reaction of stoichiometric amounts of HgBr2 and As4S4. It crystallizes in the monoclinic space group P21/c with the lattice constants a = 9.593(5) Å, b = 11.395(5) Å, c = 13.402(5) Å, β = 107.27(3)°, V = 1399(1) Å3, and Z = 2. The crystal structure consists of molecular units built from two undistorted As4S4 cages which are coordinated weakly by three almost linear HgBr2 units. Raman spectra clearly indicate minor bonding interactions between HgBr2 and As4S4.
Ge2Co6(CO)20: Ein Ge‐Co‐Cluster ausgehend von gelöstem GeBr
Authors: Schroeder Melanie , Schnepf Andreas
Published: April 2007

Ge2Co6(CO)20: A Ge‐Co Cluster Compound from Solubilized GeBr

The Ge‐Co cluster Ge2Co6(CO)20 is synthesized from a reaction of a GeBr solution with Co2(CO)8. Isolation of suitable crystals allows the determination of the crystal structure of Ge2Co6(CO)20, being the lacking member in the row GeCo4(CO)14 – Ge2Co6(CO)20 – Ge3Co8(CO)26.
Synthesis, Structure and Characterization of a Novel One‐dimensional Tube‐like Cadmium Coordination Polymer
Authors: Ding Bin , Li Jian , Yang En‐Cui , Wang Xiu‐Guang , Zhao Xiao‐Jun
Published: April 2007

By the self‐assembly of 2‐aminobenzimidazole (L), Nadca (Nadca = dicyanamide sodium) and CdCl2, a novel one‐dimensional (1D) CdII coordination polymer [Cd(μ1,5‐dca)(μ1,3,5‐dca)L]n (1) (L = 2‐aminobenzimidazole) has been synthesized and structurally characterized by single crystal X‐ray diffraction, element analysis and FT‐IR spectra. In 1 μ1,5‐bidentate and μ1,3,5‐tridentate dca ligands bridge CdII ions to form a 1D tube‐like structure, which presents a new 1D tubular structural motif of (3.4(2))(3(2).4(2).5(3)) topology in M‐dca systems (M = metallic). Solid‐state blue fluorescence spectrum of 1 also has been determined and compared with that of free ligand.
Phase Transition and Crystal Structure of the Monomeric Europium(II) Thiolate Eu(SC36H49)2
Authors: Angelkort Joachim , van Smaalen Sander , Hauber Sven Oliver , Niemeyer Mark
Published: April 2007

Single crystal X‐ray diffraction of Eu(SC36H49)2 has revealed a first order phase transition at a temperature of 119 K, that involves a reduction of the specific volume by 1 %. The transition corresponds to a doubling of the unit cell, as it is the result from reorientations of isopropyl groups that appear at peripheral sites of the organic ligands. It is argued that a denser packing is achieved at the expense of a less favourable conformation of one of the two crystallographically‐independent complexes in the low‐temperature phase. The Bond‐Valence method is used to show that interactions of equal strengths are present between europium and both sulphur atoms and both coordinating phenyl rings.
New Structure Type among Octahydrated Rare‐Earth Sulfates, β‐Ce2(SO4)3·8H2O, and a new Ce2(SO4)3·4H2O Polymorph
Authors: Casari Barbara M. , Langer Vratislav
Published: April 2007

Syntheses, crystal structures and thermal behavior of two new hydrated cerium(III) sulfates are reported, Ce2(SO4)3·4H2O (I) and β‐Ce2(SO4)3·8H2O (II), both forming three‐dimensional networks. Compound I crystallizes in the space group P21/n. There are two non‐equivalent cerium atoms in the structure of I, one nine‐ and one ten‐fold coordinated to oxygen atoms. The cerium polyhedra are edge sharing, forming helically propagating chains, held together by sulfate groups. The structure is compact, all the sulfate groups are edge‐sharing with cerium polyhedra and one third of the oxygen atoms, belonging to sulfate groups, are in the S–Oμ3–Ce2 bonding mode. Compound II constitutes a new structure type among the octahydrated rare‐earth sulfates which belongs to the space group Pn. Each cerium atom is in contact with nine oxygen atoms, these belong to four water molecules, three corner sharing and one edge sharing sulfate groups. The crystal structure is built up by layers of [Ce(H2O)4(SO4)]nn+ held together by doubly edge sharing sulfate groups. The dehydration of II is a three step process, forming Ce2(SO4)3·5H2O, Ce2(SO4)3·4H2O and Ce2(SO4)3, respectively. During the oxidative decomposition of the anhydrous form, Ce2(SO4)3, into the final product CeO2, small amount of CeO(SO4) as an intermediate species was detected.
Synthesen und Strukturen von Bis(4,4′‐t‐butyl‐2,2′‐bipyridin)‐Ruthenium(II)‐Komplexen mit funktionellen Derivaten des Tetramethyl‐bibenzimidazols
Authors: Grüßing André , Rau Sven , Schebesta Sebastian , Scholz Alexander , Görls Helmar , Walther Dirk
Published: April 2007

Syntheses and Structures of Bis(4,4′‐t‐butyl‐2,2′‐bipyridine) Ruthenium(II) Complexes with functional Derivatives of Tetramethyl‐bibenzimidazole

[(tbbpy)2RuCl2] reacts with dinitro‐tetramethylbibenzimidazole (A) in DMF to form the complex [(tbbpy)2Ru(A)](PF6)2 (1a) (tbbpy: bis(4,4′‐t‐butyl)‐2,2′bipyridine). Exchange of the two PF6− anions by a mixture of tetrafluor‐terephthalat/tetrafluor‐terephthalic acid results in the formation of 1b in which an extended hydrogen‐bonded network is formed. According to the 1H NMR spectra and X‐ray analyses of both 1a and 1b, the two nitro groups of the bibenzimidazole ligand are situated at the periphery of the complex in cis position to each other. Reduction of the nitro groups in 1a with SnCl2/HCl results in the corresponding diamino complex 2 which is a useful starting product for further functionalization reactions. Substitution of the two amino groups in 2 by bromide or iodide via Sandmeyer reaction results in the crystalline complexes [(tbbpy)2Ru(C)](PF6)2 and [(tbbpy)2Ru(D)](PF6)2 (C: dibromo‐tetrabibenzimidazole, D: diiodo‐tetrabibenzimidazole). Furthermore, 2 readily reacts with 4‐t‐butyl‐salicylaldehyde or pyridine‐2‐carbaldehyde under formation of the corresponding Schiff base RuII complexes 5 and 6. 1H NMR spectra show that the substituents (NH2, Br, I, azomethines) in 2 ‐ 6 are also situated in peripheral positions, cis to each other. The solid state structure of both 2, and 3, determined by X‐ray analyses confirm this structure. In addition, the X‐ray diffraction analyses of single crystals of the complexes [(tri‐t‐butyl‐terpy)(Cl)Ru(A)] (7) and [(A)PtCl2] (8) display also that the nitro groups in these complexes are in a cis‐arrangement.
Diethylenetriammonium Aquapentachloroferrate(III) Chloride: Structure and Magnetic Properties
Authors: James Bruce D. , Mrozinski Jerzy , Klak Julia , Skelton Brian W. , White Allan H.
Published: April 2007

Diethylenetriamine (dien) and iron(III) chloride in aqueous HCl yield (dienH3) [FeCl5(H2O)]Cl, in which the chloroferrate(III) anion is significantly distorted from octahedral symmetry due to the extensively hydrogen‐bonded lattice. On cooling, the high spin FeIII material shows weak antiferromagnetic coupling that results in a Néel temperature of 2.70 K.
Stabilizing the LaCoAl4 Structure through Indium‐Magnesium Substitution in CeRhIn4−xMgx (x = 0.79 and 0.84) – An Indide with Magnesium Centered Indium Cubes
Authors: Tuncel Selcan , Hoffmann Rolf‐Dieter , Pöttgen Rainer
Published: April 2007

The intermetallic compounds CeRhIn4−xMgx (x = 0.79 and 0.84) were prepared from the elements in sealed tantalum ampoules in a high‐frequency furnace. The samples were investigated by X‐ray powder and single crystal diffraction: LaCoAl4 type, Pmma, a = 829.5(2), b = 433.56(9), c = 740.2(2) pm, wR2 = 0.0458, 651 F2 values, 25 variables for CeRhIn3.21Mg0.79 and a = 831.44(10), b = 433.49(10), c = 741.04(10) pm, wR2 = 0.0543, 915 F2 values, 25 variables for CeRhIn3.16Mg0.84. The indium atoms build up two‐dimensional networks perpendicular to the b axis in an AA stacking sequence leaving slightly distorted trigonal, square and pentagonal prismatic voids for the rhodium, magnesium, and cerium atoms. Both square prismatic voids show small magnesium/indium mixing. The shortest interatomic distances occur for the Rh–Mg contacts (257 pm). Together, the rhodium, indium, and magnesium atoms build up three‐dimensional [RhIn4−xMgx] networks in which the cerium atoms fill distorted pentagonal channels.
Synthesis and Structure of Europium Aluminium Garnet (EAG)
Authors: Garskaite Editha , Sakirzanovas Simas , Kareiva Aivaras , Glaser Jochen , Meyer H.‐Jürgen
Published: April 2007

Europium aluminium garnet (Eu3Al5O12, EAG) was synthesized by an aqueous sol‐gel process and subsequent thermal annealing at 800 – 850 °C. Eu3Al5O12 crystallizes cubic (${\rm (} Ia \bar{\mathit 3} d, {\rm a = 12.140(1)\AA)}$ and its crystal structure was refined from X‐ray powder data. The refined oxygen position in the structure of EAG yields four shorter and four longer distances between europium and the eight surrounding oxygen atoms, forming a distorted dodecahedron. Pure Eu3Al5O12 can be treated at temperatures around 1000 °C before it converts into perovskite‐like EAP near 1300 °C.
Synthesis and Characterization of Water‐Soluble Zinc, Cobalt(II) and Copper(II) Complexes with a Neutral Tripodal N,N,N‐Ligand: Crystal Structures of [(κ3N‐4‐TIPOiPr)Co(H2O)(κ2O‐NO3)]NO3 and [(κ3N‐4‐TIPOiPr)Cu(H2O)(κO‐SO4)], 4‐TIPOiPr = tris(2‐isopropylimidazol‐4(5)‐yl)phosphane oxide
Authors: Kunz Peter C. , Zribi Alya , Frank Walter , Kläui Wolfgang
Published: April 2007

The development of ligands bearing substituents to model a hydrophobic enzyme cavity and concurrently showing sufficient solubility in aqueous media seems somehow paradox. The zinc and cobalt(II) nitrato (4, 5) and copper(II) sulfato (6) complexes of the new tris(2‐isopropylimidazol‐4(5)‐yl)phosphane oxide ligand (4‐TIPOiPr, 2a) show exactly these properties; in addition, the structure of the CoII complex 5·MeOH·Et2O shows striking similarity to the active site of CoII‐substituted carbonic anhydrase. 2a and its metal complexes are stable towards hydrolysis which is in contrast to the known sensitivity of (imidazol‐2‐yl)phosphane oxides.
(TlMes2)[BF4] – Ein Salz mit linearem (Mes‐Tl‐Mes)+‐Ion
Authors: Kuzu Istemi , Neumüller Bernhard
Published: April 2007

(TlMes2)[BF4] – A Salt with the Linear Cation (Mes‐Tl‐Mes)+

TlMes3 was reacted with [BF3(OEt2)] in Et2O at 20 °C to give (TlMes2)[BF4] (1). 1 was characterized by NMR techniques, IR spectroscopy as well as by an X‐ray structure determination. According to this, 1 is built‐up by ifinite chains of cations and anions along [001]. The linear cations are rotated 90° to each other along the chains due to the coordination of the [BF4]− ion.
Replacement of Trimethylamine in Trimethylamine‐trispentafluoroethyl‐borane. Structures of [(C2F5)3BNMe3], [NMe4][(C2F5)3BOH], and K[(C2F5)3BCH2(CO)C6H5]
Authors: Bernhardt Eduard , Brauer David J. , Köckerling Martin , Pawelke Gottfried
Published: April 2007

Trimethylamine‐tris(pentafluoroethyl)borane [(C2F5)3BNMe3] (1) reacts at 190 °C with water under displacement of the trimethylamine ligand to yield the hydroxy‐tris(pentafluoroethyl)borate [(C2F5)3BOH]− (2). In tributylamine 1 reacts with alkynes HC≡CR to form novel ethynyl‐tris(pentafluoroethyl)borate anions [(C2F5)3BC≡CR]− – R = C6H5 (3), C6H4CH3 (4), Si(CH(CH3)2)3 (5) – in moderate yields. Compound 3 adds water across the triple bond to form the novel anion [(C2F5)3BCH2(CO)C6H5]− (6). The structures of [(C2F5)3BNMe3], [NMe4][(C2F5)3BOH] and K[(C2F5)3BCH2(CO)C6H5] have been determined by x‐ray crystallography.
Synthesis, Structure, and Properties of Iron(II) and Manganese(II) Bis[Tris(1‐Ethyl‐4‐Methylimidazolyl‐κN)Phosphine] Complexes
Authors: Malkhasian Aramice Y. S. , Nikolovski Borislava , Kucera Benjamin E. , Loloee Reza , Chavez Ferman A.
Published: April 2007

FeIIL2(OTf)2 (1) and MnIIL2(OTf)2 (2) (L = tris(1‐ethyl‐4‐methylimidazolyl‐κN)phosphine; OTf= trifluoromethanesulfonate) were synthesized and their X‐ray structures were determined. Both complexes possess distorted octahedral geometry with high spin electron configuration at ambient temperature. Compound 1 exhibits a quasi‐reversible wave with E1/2 of 0.745 V versus Ag/AgNO3. Variable temperature magnetic measurements indicate that no spin‐crossover phenomenon for 1 is observed between 2.5 and 300 K. In addition, a plot of 1/χM versus T(K) is linear with a Curie constant of 3.48 emu mol−1 K.