Ronny Straube

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The mean first passage time (MFPT) is calculated for a Brownian particle in a spherical domain in R that contains N small non-overlapping absorbing windows, or traps, on its boundary. For the unit sphere, the method of matched asymptotic expansions is used to derive an explicit three-term asymptotic expansion for the MFPT for the case of N small locally(More)
A common scenario in cellular signal transduction is that a diffusing surface-bound molecule must arrive at a localized signaling region on the cell membrane before the signaling cascade can be completed. The question then arises of how quickly such signaling molecules can arrive at newly formed signaling regions. Here, we attack this problem by calculating(More)
Purple non-sulfur bacteria (Rhodospirillaceae) have been extensively employed for studying principles of photosynthetic and respiratory electron transport phosphorylation and for investigating the regulation of gene expression in response to redox signals. Here, we use mathematical modeling to evaluate the steady-state behavior of the electron transport(More)
The inhibition of viremia and p24 core antigenemia in patients infected with human immunodeficiency virus (HIV) was evaluated in separate multicenter, double-blind, placebo-controlled trials of zidovudine and ribavirin. Of 29 patients (14 with AIDS and 15 with AIDS-related complex [ARC]) enrolled in the zidovudine study, 16 received 250 mg of zidovudine(More)
Ceftriaxone, a cephalosporin with an extended half-life and excellent antibacterial activity was used to treat bacterial meningitis, given as a single daily intravenous dose of 100 mg/kg on day one, followed by 80 mg/kg daily. A total of 22 patients were treated, of whom 14 had Haemophilus influenzae type b, five had Streptococcus pneumoniae and three(More)
Biomembranes consist of a lipid bi-layer into which proteins are embedded to fulfill numerous tasks in localized regions of the membrane. Often, the proteins have to reach these regions by simple diffusion. Motivated by the observation that IP3 receptor channels (IP3R) form clusters on the surface of the endoplasmic reticulum (ER) during ATP-induced calcium(More)
Eighteen children from 3 weeks to 6.9 years of age were given an oral acyclovir suspension for herpes simplex or varicella-zoster virus infections. Thirteen patients who were 6 months to 6.9 years old received 600 mg/m2 per dose, and three infants and two children less than 2 years old were given 300 mg/m2 per dose. The drug was given four times a day,(More)
Two-component signal transduction systems, where the phosphorylation state of a regulator protein is modulated by a sensor kinase, are common in bacteria and other microbes. In many of these systems, the sensor kinase is bifunctional catalyzing both, the phosphorylation and the dephosphorylation of the regulator protein in response to input signals.(More)
Regulation by covalent modification is a common mechanism to transmit signals in biological systems. The modifying reactions are catalyzed either by two distinct converter enzymes or by a single bifunctional enzyme (which may employ either one or two catalytic sites for its opposing activities). The reason for this diversification is unclear, but(More)
We present a numerical method to identify possible candidates for quasi-stationary manifolds in complex reaction networks governed by systems of ordinary differential equations. Inspired by singular perturbation theory, we examine the ratios of certain components of the reaction rate vector. Those ratios that rapidly approach a nearly constant value define(More)