Functional properties of milk proteins as affected by Maillard reaction induced oligomerisation

Milk proteins were modified by Maillard reaction with glucose, lactose, pectin and dextran and analysed for changes in molar mass distribution and functional properties. The study revealed that oligomeric (20,000–200,000 g/mol) and polymeric (>200,000 g/mol) Maillard reaction products with heterogeneous functional property profiles were generated. Compared to untreated milk proteins, milk protein/saccharide Maillard products formed highly viscous solutions and performed increased antioxidant capacity. Improved heat stability was detected for milk protein/dextran products, higher surface hydrophobicity for milk protein/glucose and milk protein/lactose products, and increased overrun for milk protein/pectin and milk protein/dextran products. Total milk protein/saccharide Maillard products formed outstandingly stable protein foams, Maillard products of total milk protein and glucose, lactose or pectin stable O/W-emulsions. Milk protein/pectin and milk protein/dextran Maillard products were characterized by increased emulsifying activity, and whey protein/saccharide products by enhanced pancreatic in vitro digestibility.The study characterizes Maillard reaction products of milk proteins and makes it possible to specifically select modified proteins for industrial applications according to the requirements towards food proteins, weighing changes in techno- and tropho-functional protein properties.     

Visualizing dimensionality reduction of systems biology data

One of the challenges in analyzing high-dimensional expression data is the detection of important biological signals. A common approach is to apply a dimension reduction method, such as principal component analysis. Typically, after application of such a method the data is projected and visualized in the new coordinate system, using scatter plots or profile plots. These methods provide good results if the data have certain properties which become visible in the new coordinate system but which were hard to detect in the original coordinate system. Often however, the application of only one method does not suffice to capture all important signals. Therefore several methods addressing different aspects of the data need to be applied. We have developed a framework for linear and non-linear dimension reduction methods within our visual analytics pipeline SpRay. This includes measures that assist the interpretation of the factorization result. Different visualizations of these measures can be combined with functional annotations that support the interpretation of the results. We show an application to high-resolution time series microarray data in the antibiotic-producing organism Streptomyces coelicolor as well as to microarray data measuring expression of cells with normal karyotype and cells with trisomies of human chromosomes 13 and 21.     

An indentation system for determination of viscoplastic stress-strain behavior of small metal volumes before and after irradiation

The development of fusion materials for the first wall in future fusion reactors requires methods for the investigation of irradiation effects on the mechanical properties of materials which are only available in small volumes. Depth and force reading hardness measurement (or indentation) is one of the candidates that have the potential to extract valuable information on the stress-strain behavior of a material. A modified commercial indentation device installed in a hot cell of a fusion materials laboratory (FML) in combination with a neural network based analysis method allows identifying the material parameters of a unified viscoplasticity model with nonlinear isotropic and kinematic hardening from small metal specimens. By investigation of the same material before and after irradiation the method provides the possibility to separate irradiation effects on modulus, hardening and viscous behavior.     

Design and analysis of bit interleaved coded space-time modulation

Bit interleaved coded space-time modulation (BIC- STM) is an attractive strategy to achieve high power- and bandwidth-efficiency over multiple-input and multiple-output (MIMO) fading channels due to coding and diversity gains promised by the serial concatenation of an outer convolutional code, a bitwise interleaver and an inner high order space-time modulation (STM). In this paper, BICSTM with iterative decoding (BICSTM-ID) including non-iterative decoding as a special case is considered. For designing the inner STM, two parameters based on bitwise pairwise error probabilities (b- PEP) for the cases with and without a-priori knowledge are proposed as new measures for designing labeling rules for the STM codewords set suited to iterative decoding. On the other hand, the BICSTM-ID scheme is analyzed from an information theoretical aspect, and Information Processing Characteristic (IPC) analysis is developed for MIMO systems in order to fully characterize the BICSTM-ID scheme based on a new equivalent model of combined binary input channels. The analysis results show that the IPC analysis offers a unified perspective for BICSTM and BICSTM-ID from an information theoretical point of view and provides a comprehensive insight into the whole BICSTM-ID scheme as well. Additionally, IPC based upper and lower bounds on bit error ratio (BER) performance are extended to BICSTM-ID, and are confirmed by simulations. These bounds are of significant practical interest for estimating the BER performance of the bit-interleaved concatenated schemes with general nonlinear inner systems.     

Zum Einfluss der Filtergeschwindigkeit des Grundwassers auf die effektive Wärmeleitfähigkeit

By means of experimental investigation with a custom-built laboratory test station for measuring thermal conduction and convection, the increase in effective thermal conductivity due to the Darcy velocity in geothermal systems was investigated. The applicability of the database to in-situ geothermal systems was tested via extensive investigation at geothermal field sites. The increase in effective thermal conductivity due to groundwater flow was determined for sands of low, medium and high permeability. As a result of the study, additional recommendations have been developed for the design of groundwater-influenced geothermal systems which can complement the present directive (VDI-4640-1, 2010).     

Transfer of knowledge in knowledge management systems: unexplored issues and suggested studies

The management practice literature is replete with reports of practices being used to motivate a firm's knowledge workers to transfer knowledge into and out of the firm's computer resident knowledge repositories, ie, to participate with commitment in the firm's Knowledge Management System. Unfortunately, little is known with any certainty about which of these practices have what effects under which conditions. It appears that in many cases the practices are ill suited for the particular situations where they are employed, with unknown but perhaps sizeable losses in opportunities foregone because valuable knowledge is not as fully or completely transferred as is possible. In addition, it seems that some of these practices are likely to be interfering with the effectiveness of other practices, just as some drugs interfere with the potentially positive effects of other drugs. About these matters, our knowledge is exceeded by our ignorance. The paper identifies some major problems associated with knowledge transfer, and articulates some of the most important issues associated with these problems. Eight research questions are raised that, if answered with sound studies, would enable organisations to be more effective in their transfer of knowledge.     

The 2.2 A crystal structure of human chymase in complex with succinyl-Ala-Ala-Pro-Phe-chloromethylketone: structural explanation for its dipeptidyl carboxypeptidase specificity

Human chymase (HC) is a chymotrypsin-like serine proteinase expressed by mast cells. The 2.2 A crystal structure of HC complexed to the peptidyl inhibitor, succinyl-Ala-Ala-Pro-Phe-chloromethylketone (CMK), was solved and refined to a crystallographic R-factor of 18.4 %. The HC structure exhibits the typical folding pattern of a chymotrypsin-like serine proteinase, and shows particularly similarity to rat chymase 2 (rat mast cell proteinase II) and human cathepsin G. The peptidyl-CMK inhibitor is covalently bound to the active-site residues Ser195 and His57; the peptidyl moiety juxtaposes the S1 entrance frame segment 214-217 by forming a short antiparallel beta-sheet. HC is a highly efficient angiotensin-converting enzyme. Modeling of the chymase-angiotensin I interaction guided by the geometry of the bound chloromethylketone inhibitor indicates that the extended substrate binding site contains features that may generate the dipeptidyl carboxypeptidase-like activity needed for efficient cleavage and activation of the hormone. The C-terminal carboxylate group of angiotensin I docked into the active-site cleft, with the last two residues extending beyond the active site, is perfectly localized to make a favorable hydrogen bond and salt bridge with the amide nitrogen of the Lys40-Phe41 peptide bond and with the epsilon-ammonium group of the Lys40 side-chain. This amide positioning is unique to the chymase-related proteinases, and only chymases from primates possess a Lys residue at position 40. Thus, the structure conveniently explains the preferred conversion of angiotensin I to angiotensin II by human chymase.     

(±)-Catechin: Chemical Weapon,Antioxidant, or Stress Regulator?

(±)-Catechin is a flavan-3-ol that occurs in the organs of many plant species, especially fruits. Health-beneficial effects have been studied extensively, and notable toxic effects have not been found. In contrast, (±)-catechin has been implicated as a ‘chemical weapon’ that is exuded by the roots of Centaurea stoebe, an invasive knapweed of northern America. Recently, this hypothesis has been rejected based on (±)-catechin’s low phytotoxicity, instability at pH levels higher than 5, and poor recovery from soil. In the current study, (±)-catechin did not inhibit the development of white and black mustard to an extent that was comparable to the highly phytotoxic juglone, a naphthoquinone that is allegedly responsible for the allelopathy of the walnut tree. At high stress levels, caused by sub-lethal methanol concentrations in the medium, and a 12 h photoperiod, (±)-catechin even attenuated growth retardation. A similar effect was observed when (±)-catechin was assayed for brine shrimp mortality. Higher concentrations reduced the mortality caused by toxic concentrations of methanol. Further, when (±)-catechin was tested in variants of the deoxyribose degradation assay, it was an efficient scavenger of reactive oxygen species (ROS) when they were present in higher concentrations. This antioxidant effect was enhanced when iron was chelated directly by (±)-catechin. Conversely, if iron was chelated to EDTA, pro-oxidative effects were demonstrated at higher concentrations; in this case (±)-catechin reduced molecular oxygen and iron to reagents required by the Fenton reaction to produce hydroxyl radicals. A comparison of cyclic voltammograms of (±)-catechin with the phytotoxic naphthoquinone juglone indicated similar redox-cycling properties for both compounds although juglone required lower electrochemical potentials to enter redox reactions. In buffer solutions, (±)-catechin remained stable at pH 3.6 (vacuole) and decomposed at pH 7.4 (cytoplasm) after 24 h. The results support the recent rejection of the hypothesis that (±)-catechin may serve as a ‘chemical weapon’ for invasive plants. Instead, accumulation and exudation of (±)-catechin may help plants survive periods of stress.