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At least 1,009 records · Page 56Linked to original sources
PubMed1992

Langevin dynamics of peptides: the frictional dependence of isomerization rates of N-acetylalanyl-N'-methylamide.

The rate constant for the transition between the equatorial and axial conformations of N-acetylalanyl-N'-methylamide has been determined from Langevin dynamics (LD) simulations with no explicit solvent. The isomerization rate is maximum at collision frequency gamma = 2 ps-1, shows diffusive character for gamma greater than or equal to 10 ps-1, but does not approach zero even at gamma = 0.01 ps-1. This behavior differs from that found for a one-dimensional bistable potential and indicates that both collisional energy transfer with solvent and vibrational energy transfer between internal modes are important in the dynamics of barrier crossing for this system. It is suggested that conformational searches of peptides be carried out using LD with a collision frequency that maximizes the isomerization rate (i.e., gamma approximately 2 ps-1). This method is expected to be more efficient than either molecular dynamics in vacuo (which corresponds to LD with gamma = 0) or molecular dynamics in solvent (where dynamics is largely diffusive).

Alanine↗
PubMed1999

A General Equation for Fitting Contact Area and Friction vs Load Measurements.

The variation of contact area with load between adhesive elastic spheres depends upon the effective range of attractive surface forces. Relatively simple forms to describe limiting cases exist, but the general intermediate case requires a more complex analysis. Maugis, using a Dugdale model [D. Maugis, J. Colloid. Interf. Sci. 150, 243 (1992)], provides an analytic solution, but the resulting equations are cumbersome if one wishes to compare with experimental data such as atomic force microscope measurements. In this paper we present a simpler general equation that approximates Maugis' solution extremely closely. The general equation is amenable to conventional curve fitting software routines and provides a rapid method of determining the value of the "transition parameter" which describes the range of surface forces. Copyright 1999 Academic Press.

Journal Article↗
PubMed1995

The clinical and radiological results of revision of low friction arthroplasty in the elderly.

We assessed 130 patients (138 hips) who were more than 70 years old at the time of revision arthroplasty and had a minimum follow-up of 4 years. The average follow-up was for 7 years 3 months. The clinical results were excellent or satisfactory in 95.6% of the cases. Systemic complications developed postoperatively in 47 patients (34.1%). Radiographically, 95.6% had a well-fixed, stable stem while 91.3% had a stable socket. Seven hips (5.1%) required re-revision. Analysis revealed a 96.5% survival of the arthroplasty at 8 years.

Aged↗