Open Access. Powered by Scholars. Published by Universities.®

Biochemistry, Biophysics, and Structural Biology Commons™

Open Access. Powered by Scholars. Published by Universities.®

2004

Discipline
Institution
Keyword
Publication
Publication Type

Articles 121 - 124 of 124

Full-Text Articles in Biochemistry, Biophysics, and Structural Biology

Activation Kinetics Of Skinned Cardiac Muscle By Laser Photolysis Of Nitrophenyl-Egta, Hunter Martin, Marcus G. Bell, Graham C. Ellis-Davis, Robert J. Barsotti Jan 2004

Activation Kinetics Of Skinned Cardiac Muscle By Laser Photolysis Of Nitrophenyl-Egta, Hunter Martin, Marcus G. Bell, Graham C. Ellis-Davis, Robert J. Barsotti

PCOM Scholarly Works

The kinetics of Ca2+-induced contractions of chemically skinned guinea pig trabeculae was studied using laser photolysis of NP-EGTA. The amount of free Ca2+ released was altered by varying the output from a frequency-doubled ruby laser focused on the trabeculae, while maintaining constant total [NP-EGTA] and [Ca2+]. The time courses of the rise in stiffness and tension were biexponential at 23°C, Ph 7.1, and 200 Mm ionic strength. At full activation (pCa < 5.0), the rates of the rapid phase of the stiffness and tension rise were 56 ± 7 s-1 (n = 7) and 48 ± 6 s-1 (n = 11) while the amplitudes were 21 ± 2 and 23 ± 3%, respectively. These rates had similar dependencies on final [Ca2+] achieved by photolysis: 43 and 50 s-1 per Pca unit, respectively, over a range of [Ca2+] producing from 15% to 90% of maximal isometric tension. At all [Ca2+], the rise in stiffness initially was faster than that of tension. The maximal rates for the slower components of the rise in stiffness and tension were 4.1 ± 0.8 and 6.2 ± 1.0 s-1. The rate of this slower phase exhibited significantly less Ca2+ sensitivity, 1 and 4 s-1 per Pca unit for stiffness and tension, respectively. These data, along with previous studies indicating that the force-generating step in the cross-bridge cycle of cardiac muscle is marginally sensitive to [Ca2+], suggest a mechanism of regulation in which Ca2+ controls the attachment step in the cross-bridge cycle via a rapid equilibrium with the thin filament activation state. Myosin kinetics sets the time course for the rise in stiffness and force generation with the biexponential nature of the mechanical responses to steps in [Ca2+] arising from a shift to slower cross-bridge kinetics as the number of strongly bound cross-bridges increases.

Go to article

Theoretical Neuroscience: Modeling The Activation Mechanism Of Potassium Channels In Neurons, Kevin Twedt Jan 2004

Theoretical Neuroscience: Modeling The Activation Mechanism Of Potassium Channels In Neurons, Kevin Twedt

Presidential Scholars Theses (1990 – 2006)

We have modeled the electrostatic interaction between the S4 segment of the potassium channel molecule and the surrounding water molecules on both the intracellular and extracellular sides of the neural axon cell membrane. Two methods were used to approximate this interaction: (i) a macroscopic evaluation in which the water was treated as a dielectric medium with dielectric constant 80; (ii) a microscopic evaluation considering the effects of each individual water molecule fixed in position within the water pockets surrounding the S4 segment. The potential energy of the S4 due to the water pockets was plotted against the rotation of the …

Go to article

Influence Of Short-Term Variations In Food On Survival Of Crassotrea Gigas Larvae: A Modeling Study, Eric N. Powell, Eleanor A, Bochenek, John M. Klinck, Eileen E. Hofmann Jan 2004

Influence Of Short-Term Variations In Food On Survival Of Crassotrea Gigas Larvae: A Modeling Study, Eric N. Powell, Eleanor A, Bochenek, John M. Klinck, Eileen E. Hofmann

OES Faculty Publications

A biochemically-based model was developed to simulate the growth, development, and metamorphosis of larvae of the Pacific oyster, Crassostrea gigas. The model defines larvae in terms of their protein, lipid, carbohydrate, and ash content and includes variation in growth efficiency and egg quality to better simulate cohort population dynamics. Changes in tissue composition occur as the larva grows and in response to the biochemical composition of the food. The premise behind this modeling study was that certain periods of larval life are more critical than others with respect to the availability of food and that food quality is as …

Go to article

Aminoacyl-Trnas: Setting The Limits Of The Genetic Code, Michael Ibba, Dieter Söll Jan 2004

Aminoacyl-Trnas: Setting The Limits Of The Genetic Code, Michael Ibba, Dieter Söll

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Aminoacyl-tRNAs (aa-tRNAs) are simple molecules with a single purpose—to serve as substrates for translation. They consist of mature tRNAs to which an amino acid has been esterified at the 3′-end. The 20 different types of aa-tRNA are made by the 20 different aminoacyl-tRNA synthetases (aaRSs, of which there are two classes), one for each amino acid of the genetic code (Ibba and Söll 2000). This would be fine if it were not for the fact that such a straightforward textbook scenario is not true in a single known living organism. aa-tRNAs lie at the heart of gene expression; they interpret …

Go to article

First Prev