Statistical modeling, nuclear magnetic resonance

Because this problem is complex several avenues of attack have been devised in the last fifteen years. A combination of experimental developments (protein engineering, advances in x-ray and nuclear magnetic resonance (NMR), various time-resolved spectroscopies, single molecule manipulation methods) and theoretical approaches (use of statistical mechanics, different computational strategies, use of simple models) [5, 6 and 7] has led to a greater understanding of how polypeptide chains reach the native confonnation. 

Carbon-13 nuclear magnetic resonance was used to determine the molecular structure of four copolymers of vinyl chloride and vinylidene chloride. The spectra were used to determine both monomer composition and sequence distribution. Good agreement was found between the chlorine analysis determined from wet analysis and the chlorine analysis determined by the C nmr method. The number average sequence length for vinylidene chloride measured from the spectra fit first order Markovian statistics rather than Bernoullian. The chemical shifts in these copolymers as well as their changes in areas as a function of monomer composition enable these copolymers to serve as model... 

The dynamics of the so-called biological water molecules in the immediate vicinity of a protein have been studied using dielectric relaxation [18], proton and O NMR relaxation [19], reaction path calculation [20], and analytical statistical mechanical models [21]. While the dielectric relaxation time of ordinary water molecules is 10 ps [16], both the dielectric [18] and nuclear magnetic resonance (NMR) relaxation studies [19], indicate that near the protein surface the relaxation dynamics are bimodal with two components in the 10-ns and 10-ps time scale, respectively. The 10-ns relaxation time cannot be due to the motion of the peptide chains, which occurs in the 100-ns time scale. From the study of NMR relaxation times of " O at the protein surface, Halle et al. [19c,d] suggested dynamic exchange between the slowly rotating internal and the fast external water molecules. 

Additional confirmation of the statistical model comes from experiments of a quite different nature involving nuclear magnetic resonance. The protons in the water molecule possess a nuclear magnetic moment so that their environment can be investigated by studies of the shape of their resonant absorption line in a steady applied magnetic field. In an isolated water molecule the resonance is very sharp and this is also the case in liquid water for, although... 

See alsor. Chemometrics and Statistics Statistical Techniques Expert Systems Multicriteria Decision Making. Computer Modeling. Nuclear Magnetic Resonance Spectroscopy Techniques Multidimensional Proton. 

Spectroscopic Methods.—Nuclear Magnetic Resonance (n.m.r.). Cohen-Addad and Ruby comment that thermodynamic polymer-solvent interaction parameters obtained from n.m.r. data should be contrasted with those obtained from other methods in the sense that the former are defined on a molecular scale only. That is, nuclear spins are local probes, sensitive to magnetic interactions averaged over volumes of molecular size. N.m.r. methods, therefore, usefully complement other methods in studying underlying statistical mechanical models for polymer-solvent mixtures at equilibrium a comment which has been amplified in relation to polymer blends. ... 

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