1,721,011 research outputs found
Report on the first maga circe conference on metabolic systems analysis
No full text[No abstract available
Application of trilinear SLICING to analyse a single relaxation curve
No full textDetermining the time constants and amplitudes of exponential decays from relaxation data is a common task in LF-NMR. In this communication, we present an application of the SLICING algorithm to evaluate its possibilities for solving this problem. The method, originally introduced to compare different samples, is applied here to analyse a single relaxation curve, using the embedding technique. To test this procedure, we acquired data sets from samples of liquids properly separated, and characterized by different relaxation times. The results show a good estimation of parameters, comparable with those obtained applying Marquardt's algorithm, when the components have sufficiently different relaxation times. © 2004 Elsevier Inc. All rights reserved
Elucidating protein secondary structures using alpha-carbon recurrence quantifications
No full textSecondary structures of proteins were studied by recurrence quantification analysis (RQA). High-resolution, 3-dimensional coordinates of alpha-carbon atoms comprising a set of 68 proteins were downloaded from the Protein Data Bank. By fine-tuning four recurrence parameters (radius, line, residue, separation), it was possible to establish excellent agreement between percent contribution of alpha-helix and beta-sheet structures determined independently by RQA and that of the DSSP algorithm (Define Secondary Structure of Proteins). These results indicate that there is an equivalency between these two techniques, which are based upon totally different pattern recognition strategies. RQA enhances qualitative contact maps by quantifying the arrangements of recurrent points of alpha carbons close in 3-dimensional space. For example, the radius was systematically increased, moving the analysis beyond local alpha-carbon neighborhoods in order to capture super-secondary and tertiary structures. However, differences between proteins could only be detected within distances up to about 6-11 Å, but not higher. This result underscores the complexity of alpha-carbon spacing when super-secondary structures appear at larger distances. Finally, RQA-defined secondary structures were found to be robust against random displacement of alpha carbons upwards of 1 Å This finding has potential import for the dynamic functions of proteins in motion. ©2001 Wiley-Liss, Inc
Methods using recurrence quantification analysis to analyze and generate images.
No full textMethods for identifying and quantifying recurrent and deterministic patterns in digital images are provided. The methods, which are based on Recurrence Quantification Analysis (RQA), generate similarity or dissimilarity distance matrices for digital images that may be used to calculate a variety of quantitative characteristics for the images. Also provided are methods for identifying and imaging spatial distributions of time variable signals generated from dynamic systems. In these methods a time variable signal is recorded for a plurality of area or volume elements into which a dynamic system has been sectioned and RQA is used to calculate one or more RQA variables for each of the area or volume elements, which may then be used to generate a two or three dimensional image displaying the spatial distribution of the RQA variables across the system
Invariant features of metabolic networks: a data analysis application on scaling properties of biochemical pathways
No full textThe network metaphor is currently one of the most common general paradigms in biological sciences: this paradigm spans different scales of definition going from gene regulation to protein-protein interaction studies and metabolic regulation networks. Generally, the networks are defined by the nature of the connected elements (nodes) and their relative relations (edges). In this paper we demonstrate how the same biochemical regulation network can assume different shapes in terms of both constituting elements and intervening relations while remaining recognizable as a specific entity. This behaviour can be explained by the general scaling properties of biological networks and points to regulation pathways as emergent features of biochemical systems posited at a different hierarchical level with respect to the intervening metabolites. (C) 2004 Elsevier B.V. All rights reserved
Singular hydrophobicity patterns and net charge: a mesoscopic principle for protein aggregation/folding
No full textA statistical model describing the propensity for protein aggregation is presented. Only amino-acid hydrophobicity values and calculated net charge are used for the model. The combined effects of hydrophobic patterns as computed by the signal analysis technique, recurrence quantification, plus calculated net charge were included in a function emphasizing the effect of singular hydrophobic patches which were found to be statistically significant for predicting aggregation propensity as quantified by fluorescence studies obtained from the literature. These results suggest preliminary evidence for a mesoscopic principle for protein folding/aggregation. (C) 2004 Elsevier B.V. All rights reserved
Musical Consonance can be Inferred from intervals formed with pure tones using nonlinear analysis
No full textOn the Possibility That We Think in a Quantum Mechanical Manner : An Experimental Verification of Existing Quantum Interference Effects In Cognitive Anomaly of Conjunction Fallacy
No full textRecurrence analysis of hydration effects on nonlinear protein dynamics: multiplicative scaling and additive processes
No full textThe potential energy time series obtained from molecular dynamics simulations of the B1 domain of protein G and plastocyanin both in vacuo and in water were analyzed by means of recurrence quantification analysis. This methodology is robust for nonlinear, nonstationary processes, and demonstrated the existence of a flat recurrence spectrum occurring beyond a previously described scaling region of protein dynamics, as well as the existence of clustered modes of very long period (approximately 500 ps) elicited by the solvent. The number of these modes was approximately related to the number of structural domains of the studied proteins. Thus the methodology may be useful to distinguish processes intrinsic to protein folding dynamics from those which develop from hydration. (C) 2001 Elsevier Science B.V. All rights reserved
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