Structure of Rab GDP-dissociation inhibitor in complex with prenylated YPT1 GTPase

Rab/Ypt guanosine triphosphatases (GTPases) represent a family of key membrane traffic regulators in eukaryotic cells whose function is governed by the guanosine diphosphate (GDP) dissociation inhibitor (RabGDI). Using a combination of chemical synthesis and protein engineering, we generated and crystallized the monoprenylated Ypt1:RabGDI complex. The structure of the complex was solved to 1.5 angstrom resolution and provides a structural basis for the ability of RabGDI to inhibit the release of nucleotide by Rab proteins. Isoprenoid binding requires a conformational change that opens a cavity in the hydrophobic core of its domain II. Analysis of the structure provides a molecular basis for understanding a RabGDI mutant that causes mental retardation in humans.     

REVIEW: Aroma of Wheat Bread Crumb

Bread aroma is an important parameter for bread quality, and this review aims to provide an overview of aroma compounds identified in bread crumb and how these compounds are formed. More than 150 volatile compounds were identified in bread crumb, and they mainly originated from the fermentative activity of yeast, from oxidation of flour lipids, and to a lower extent from Maillard reactions. Of those volatile compounds, 45 compounds can be characterized as aroma compounds, because they most likely can be sensed when the bread is eaten because of their high odor activity values and flavor dilution factors. The influence of ingredients and mixing conditions on bread aroma has scarcely been investigated. The fermentation conditions (yeast level and strain as well as fermentation temperature and time) were found to significantly influence the aroma of bread crumb. Yeast level and strain mainly influence formation of compounds directly related to the fermentative activity of yeast, whereas fermentation temperature and time also influence formation of compounds from oxidation of flour lipids.     

SONOGRAPHIC INVESTIGATIONS OF THE GASTROINTESTINAL TRACT OF GRANIVOROUS BIRDS

This article describes the sonographic examination of the normal gastrointestinal tract of granivorous birds. Preliminary tests with dead birds were performed to get an idea of the sonographic echotexture of the avian gastrointestinal tract. Later, clinically healthy seedeaters of different weights were examined sonographically. As equipment a convex microcurved scanner with a particularly small coupling surface and an adjustable frequency from 5.5-7.5 MHz was used. For the investigation of the gastrointestinal tract, six sonographic approaches are described. After a starving time of 18 hours in the granivorous birds and water input, the best sonographic image quality could be obtained. Using this method, the crop, ventriculus, intestines, and cloaca could be demonstrated sonographically; whereas, it was not possible to visualize the normal proventriculus in granivorous birds. In contrast to mammals, the different layers of the wall of the gastrointestinal tract could not be visualized with the equipment used. Motility of individual parts of the gastrointestinal tract (GI tract), however, could be well demonstrated.