Although originally designed for broadband inversion and decoupling in NMR spectroscopy, recent methodological developments have introduced adiabatic fast passage (AFP) pulses into the field of protein dynamics. AFP pulses employ a frequency sweep, and have not only superior inversion properties with respect to offset effects, but they are also easily implemented into a pulse sequence. As magnetization is dragged from the +z to the -z direction, Larmor precession is impeded since magnetization becomes spin-locked, which is a potentially useful feature for the investigation of microsecond to millisecond dynamics.
View Article and Find Full Text PDFOsteopontin (OPN) is an acidic hydrophilic glycophosphoprotein that was first identified as a major sialoprotein in bones. It functions as a cell attachment protein displaying a RGD cell adhesion sequence and as a cytokine that signals through integrin and CD44 cell adhesion molecules. OPN is also implicated in human tumor progression and cell invasion.
View Article and Find Full Text PDFCarr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion NMR spectroscopy has emerged as a powerful tool for quantifying the kinetics and thermodynamics of millisecond exchange processes between a major, populated ground state and one or more minor, low populated and often invisible 'excited' conformers. Analysis of CPMG data-sets also provides the magnitudes of the chemical shift difference(s) between exchanging states (|Deltavarpi|), that inform on the structural properties of the excited state(s). The sign of Deltavarpi is, however, not available from CPMG data.
View Article and Find Full Text PDFAnalysis of Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion NMR profiles provides the kinetics and thermodynamics of millisecond-time-scale exchange processes involving the interconversion of populated ground and invisible excited states. In addition, the absolute values of chemical shift differences between NMR probes in the exchanging states, |Delta omega|, are also extracted. Herein, we present a simple experiment for obtaining the sign of (1)H(alpha) Delta omega values by measuring off-resonance (1)H(alpha) decay rates, R(1rho), using weak proton spin-lock fields.
View Article and Find Full Text PDFA novel spectral entropy interpretation for protein NOESY data is presented for the investigation of the spatial distribution of residues in protein structures without the requirement of NOE cross peak assignments. In this approach individual traces S(i)(omega) from a 3D (15)N NOESY-HSQC taken at frequency positions corresponding to different amide groups (residue position i) are subjected to a self-convolution procedure thus leading to the autocorrelation function C(i)(omega) of the NOESY-trace for a particular backbone residue position. The characteristic spatial surrounding of a particular residue position is reflected in the corresponding autocorrelation function and can be quantified by taking the (spectral) entropy S(nu) as an information measure.
View Article and Find Full Text PDFDirect methods in NMR based structure determination start from an unassigned ensemble of unconnected gaseous hydrogen atoms. Under favorable conditions they can produce low resolution structures of proteins. Usually a prohibitively large number of NOEs is required, to solve a protein structure ab-initio, but even with a much smaller set of distance restraints low resolution models can be obtained which resemble a protein fold.
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