Observation of Fragile-to-Strong Dynamic Crossover in Protein Hydration Water

At low temperatures proteins exist in a glassy state, a state which has no conformational flexibility and shows no biological functions. In a hydrated protein, at and above 220 K, this flexibility is restored and the protein is able to sample more conformational sub-states, thus becomes biologically functional. This 'dynamical' transition of protein is believed to be triggered by its strong coupling with the hydration water, which also shows a similar dynamic transition. Here we demonstrate experimentally that this sudden switch in dynamic behavior of the hydration water on lysozyme occurs precisely at 220 K and can be described as a Fragile-to-Strong dynamic crossover (FSC). At FSC, the structure of hydration water makes a transition from predominantly high-density (more fluid state) to low-density (less fluid state) forms derived from existence of the second critical point at an elevated pressure.Comment: 6 pages (Latex), 4 figures (Postscript

CHOLANE AND LANOSTANE DERIVATIVES: ANTIMICROBIAL EVALUATION

Steroids are natural compounds with several important applications in many fields of research, such as medicinal chemistry, pharmacology, supramolecular chemistry and nanotechnology.In particular, bile acids such as lithocholic acid (LCA) and ursodeoxycholic acid (UDCA) have been considered quite useful as starting points for a rich and different set of medicinal chemistry activities. Besides, the discovery of bioactive ingredients from plants and fungi is always the main target in medicinal chemistry. The lanostane-type triterpenoid 3b-hydroxylanosta-8,24-diene-21-oic acid (Trametenolic acid, TMA) was the main bioactive component of Gloeophyllum odoratum, which was reported to possess widely bioactivities, including tumor cell anti-proliferation effects (for example, human HL-60 leukemia, human KB epidermoid carcinoma, murine L1210 leukemia cells, Caski, HT-3, T-24, etc.), inhibition of enzyme activity (human thrombin, bovine trypsin and so on).Nevertheless, trametenolic acid was scarcely investigated as antimicrobial agent. Structurally, bile acids (LCA and UDCA) and trametenolic acid are similar since they may be regarded as consisting of two components, a rigid steroid nucleus and an aliphatic side chain possessing a carboxyl group. On the basis of these considerations, six new compounds bearing a guanidine moiety in their side chain were synthesized using LCA, UDCA and TMA as starting materials. The parent bile acids, TMA and their resulting derivatives were evaluated for antimicrobial activity against S. aureus, B. subtilis and M. smegmatis. The derivative 3a-hydroxy-23-guanidino-5b-cholane showed the best activity, with MIC values of 12.5 \u3bcM against S. aureus, 5 \u3bcM against B. subtilis and 50 \u3bcM against M. smegmatis. The cytotoxic activity of bile acids, trametenolic acid and derivatives was also evaluated against HT-29 cell lin

The Spectrum of Integrated Millimeter Flux of the Magellanic Clouds and 30-Doradus from TopHat and DIRBE Data

We present measurements of the integrated flux relative to the local background of the Large and Small Magellanic Clouds and the region 30-Doradus (the Tarantula Nebula) in the LMC in four frequency bands centered at 245, 400, 460, and 630 GHz, based on observations made with the TopHat telescope. We combine these observations with the corresponding measurements for the DIRBE bands 8, 9, and 10 to cover the frequency range 245 - 3000 GHz (100 - 1220 micrometers) for these objects. We present spectra for all three objects and fit these spectra to a single-component greybody emission model and report best-fit dust temperatures, optical depths, and emissivity power-law indices, and we compare these results with other measurements in these regions and elsewhere. Using published dust grain opacities, we estimate the mass of the measured dust component in the three regions.Comment: 41 pages, 4 figures. Accepted for publication in Astrophysical Journa

Progress report on identification of "organisms" in Lake Victoria responsible for echosounder traces

Exploratory fishing with midwater trawls in the pelagic zone of Lake Victoria generally yielded low quantities of fish even where dense traces appeared on the echosounder. Efforts to identify the "organisms" met with limited success. Types of gear were tested the midwater trawl, high-speed beam trawl, Lampara net, zooplankton net and SCUBA. This information plus that of earlier investigators indicate that the bulk of the traces are not caused by fish. The evidence however is not conclusive and further studies are warranted. Some recommendations for study are presented

Cardinality constrained connected balanced partitions of trees under different criteria

In this paper we study the problem of partitioning a tree with n weighted vertices into p connected components. For each component, we measure its gap, that is, the difference between the maximum and the minimum weight of its vertices, with the aim of minimizing the sum of such differences. We present an O(n3p2) time and O(n3p) space algorithm for this problem. Then, we generalize it, requiring a minimum of ε≥1 nodes in each connected component, and provide an O(n3p2ε2) time and O(n3pε) space algorithm to solve this new problem version. We provide a refinement of our analysis involving the topology of the tree and an improvement of the algorithms for the special case in which the weights of the vertices have a heap structure. All presented algorithms can be straightforwardly extended to other similar objective functions. Actually, for the problem of minimizing the maximum gap with a minimum number of nodes in each component, we propose an algorithm which is independent of ε and requires O(n2lognp2) time and O(n2p) space

Speeding-Up Expensive Evaluations in High-Level Synthesis Using Solution Modeling and Fitness Inheritance

High-Level Synthesis (HLS) is the process of developing digital circuits from behavioral specifications. It involves three interdependent and NP-complete optimization problems: (i) the operation scheduling, (ii) the resource allocation, and (iii) the controller synthesis. Evolutionary Algorithms have been already effectively applied to HLS to find good solution in presence of conflicting design objectives. In this paper, we present an evolutionary approach to HLS that extends previous works in three respects: (i) we exploit the NSGA-II, a multi-objective genetic algorithm, to fully automate the design space exploration without the need of any human intervention, (ii) we replace the expensive evaluation process of candidate solutions with a quite accurate regression model, and (iii) we reduce the number of evaluations with a fitness inheritance scheme. We tested our approach on several benchmark problems. Our results suggest that all the enhancements introduced improve the overall performance of the evolutionary search

The TopHat experiment: A balloon-borne instrument for mapping millimeter and submillimeter emission

The TopHat experiment was designed to measure the anisotropy in the cosmic microwave background radiation on angular scales from 0.degrees 3 to 30 degrees and the thermal emission from both Galactic and extragalactic dust. The balloon-borne instrument had five spectral bands spanning frequencies from 175 to 630 GHz. The telescope was a compact, 1 m, on-axis Cassegrain telescope designed to scan the sky at a fixed elevation of 78 degrees. The radiometer used cryogenic bolometers coupled to a single feed horn via a dichroic filter system. The observing strategy was intended to efficiently cover a region 48 degrees in diameter centered on the south polar cap with a highly cross-linked and redundant pattern with nearly uniform sky coverage. The Long Duration Balloon flight over Antarctica in 2001 January surveyed about 6% of the sky. Here we describe the design of the instrument and the achieved in-flight performance and provide a brief discussion of the data analysis

Efficient GRASP+VND and GRASP+VNS metaheuristics for the traveling repairman problem

The traveling repairman problem is a customer-centric routing problem, in which the total waiting time of the customers is minimized, rather than the total travel time of a vehicle. To date, research on this problem has focused on exact algorithms and approximation methods. This paper presents the first metaheuristic approach for the traveling repairman problem

On finding connected balanced partitions of trees

Graph partitioning is a widely studied problem in the literature with several applications in real life contexts. In this paper we study the problem of partitioning a graph, with weights at its vertices, into p connected components. For each component of the partition we measure the difference between the maximum and the minimum weight of a vertex in the component. We consider two objective functions to minimize, one measuring the maximum of such differences among all the components in the partition, and the other measuring the sum of the differences between the maximum and the minimum weight of a vertex in each component. We focus our analysis on tree graphs and provide polynomial time algorithms for solving these optimization problems on such graphs. In particular, we present an O(n2logn) time algorithm for the min–max version of the problem on general trees and several, more efficient polynomial algorithms for some trees with a special structure, such as spiders and caterpillars. Finally, we present NP-hardness and approximation results on general graphs for both the objective functions

Temperature dependence of protein dynamics simulated with three different water models

The effect of variation of the water model on the temperature dependence of protein and hydration water dynamics is examined by performing molecular dynamics simulations of myoglobin with the TIP3P, TIP4P, and TIP5P water models and the CHARMM protein force field at temperatures between 20 and 300 K. The atomic mean-square displacements, solvent reorientational relaxation times, pair angular correlations between surface water molecules, and time-averaged structures of the protein are all found to be similar, and the protein dynamical transition is described almost indistinguishably for the three water potentials. The results provide evidence that for some purposes changing the water model in protein simulations without a loss of accuracy may be possible