Purdue University

About: Purdue University is a education organization based out in West Lafayette, Indiana, United States. It is known for research contribution in the topics: Population & Heat transfer. The organization has 73219 authors who have published 163563 publications receiving 5775236 citations. The organization is also known as: Purdue & Purdue-West Lafayette.

Multi-site assessment of the precision and reproducibility of multiple reaction monitoring–based measurements of proteins in plasma

Abstract: Verification of candidate biomarkers relies upon specific, quantitative assays optimized for selective detection of target proteins, and is increasingly viewed as a critical step in the discovery pipeline that bridges unbiased biomarker discovery to preclinical validation. Although individual laboratories have demonstrated that multiple reaction monitoring (MRM) coupled with isotope dilution mass spectrometry can quantify candidate protein biomarkers in plasma, reproducibility and transferability of these assays between laboratories have not been demonstrated. We describe a multilaboratory study to assess reproducibility, recovery, linear dynamic range and limits of detection and quantification of multiplexed, MRM-based assays, conducted by NCI-CPTAC. Using common materials and standardized protocols, we demonstrate that these assays can be highly reproducible within and across laboratories and instrument platforms, and are sensitive to low mug/ml protein concentrations in unfractionated plasma. We provide data and benchmarks against which individual laboratories can compare their performance and evaluate new technologies for biomarker verification in plasma.

Rainfall energy and its relationship to soil loss

Abstract: A relatively simple procedure is presented for computation of kinetic energy of a rainstorm from information on a recording-raingage chart. An equation is developed describing rainfall energy as a function of rainfall intensity. The effects of rainfall energy and its interaction with other variables are evaluated in multiple regression analyses based on data representing four soil types. Application of this information to separate the effects of rainfall from those of physical and management characteristics in plot data is discussed briefly.

Determination of amide hydrogen exchange by mass spectrometry: A new tool for protein structure elucidation

Abstract: A new method based on protein fragmentation and directly coupled microbore high-performance liquid chromatography-fast atom bombardment mass spectrometry (HPLC-FABMS) is described for determining the rates at which peptide amide hydrogens in proteins undergo isotopic exchange. Horse heart cytochrome c was incubated in D2O as a function of time and temperature to effect isotopic exchange, transferred into slow exchange conditions (pH 2-3, 0 degrees C), and fragmented with pepsin. The number of peptide amide deuterons present in the proteolytic peptides was deduced from their molecular weights, which were determined following analysis of the digest by HPLC-FABMS. The present results demonstrate that the exchange rates of amide hydrogens in cytochrome c range from very rapid (k > 140 h-1) to very slow (k < 0.002 h-1). The deuterium content of specific segments of the protein was determined as a function of incubation temperature and used to indicate participation of these segments in conformational changes associated with heating of cytochrome c. For the present HPLC-FABMS system, approximately 5 nmol of protein were used for each determination. Results of this investigation indicate that the combination of protein fragmentation and HPLC-FABMS is relatively free of constraints associated with other analytical methods used for this purpose and may be a general method for determining hydrogen exchange rates in specific segments of proteins.

The Intrinsic Bayes Factor for Model Selection and Prediction

Abstract: In the Bayesian approach to model selection or hypothesis testing with models or hypotheses of differing dimensions, it is typically not possible to utilize standard noninformative (or default) prior distributions. This has led Bayesians to use conventional proper prior distributions or crude approximations to Bayes factors. In this article we introduce a new criterion called the intrinsic Bayes factor, which is fully automatic in the sense of requiring only standard noninformative priors for its computation and yet seems to correspond to very reasonable actual Bayes factors. The criterion can be used for nested or nonnested models and for multiple model comparison and prediction. From another perspective, the development suggests a general definition of a “reference prior” for model comparison.

Evaluation of the brief questionnaire of smoking urges (QSU-brief) in laboratory and clinical settings.

Abstract: A brief, 10-item version of the Questionnaire of Smoking Urges (QSU; Tiffany & Drobes, British Journal of Addiction 86:1467-1476, 1991) was administered to 221 active cigarette smokers in a laboratory setting (Study 1) and to 112 smokers enrolled in a comprehensive smoking cessation program (Study 2). In the laboratory setting, craving to smoke was evaluated in response to neutral and smoking-related stimuli. In the clinical setting, craving was assessed prior to cessation and again during treatment. Factor analyses revealed that a two-factor solution best described the item structure of the QSU-Brief across conditions. Factor 1 items reflected a strong desire and intention to smoke, with smoking perceived as rewarding for active smokers. Factor 2 items represented an anticipation of relief from negative affect with an urgent desire to smoke. The findings were consistent with the expressions of craving found in the 32-item version of the QSU (Tiffany & Drobes, 1991). Regression analyses demonstrated stronger baseline mood intensity and self-reported tendency to smoke to achieve pleasurable effects and to experience the desire to smoke when cigarettes are unavailable were predictive of general levels of craving report in active smokers in the laboratory and clinical setting. The findings supported a multidimensional conceptualization of craving to smoke and demonstrated the utility of a brief multidimensional measure of craving.