Synthesis of macrocyclic diacyl/dialkyl glycerols containing disulfide tether and studies of their effects upon incorporation in DPPC membranes. Implications in the design of phospholipase A(2) modulators

A general method for the preparation of novel disulfide-tethered macrocyclic diacylglycerols (DAGs) has been described. Overall synthesis involved stepwise protection, acylation, and deprotection to yield the bis(omega-bromoacyl) glycerols. In the crucial macrocyclization step, a unique reagent, benzyltriethylammonium tetrathiomolybdate (BTAT), has been used to convert individual bis(omega-bromoacyl) glycerols to their respective macrocyclic disulfides. DAG 6, which had ether linkages between hydrocarbon chains and the glycerol backbone, was also synthesized from an appropriate precursor using a similar protocol. One of the DAGs (DAG 5) had a carbon-carbon tether instead of a disulfide one and was synthesized using modified Glaser coupling. Preparation of alpha-disulfide-tethered DAG (DAG 4) required an alternative method, as treatment of the bisbromo precursor with BTAT gave a mixture of several compounds from which separation of the target molecule was cumbersome. To avoid this problem, the bisbromide was converted to its corresponding dithiocyanate, which on further treatment with BTAT yielded the desired DAG (DAG 4) in good yield. Upon treatment with the reducing agent dithiothreitol (DTT), the DAGs that contain a disulfide tether could be quantitatively converted to their "open-chain" thiol analogues. These macrocyclic DAGs and their reduced "open-chain" analogues have been incorporated in DPPC vesicles to study their effect on model membranes. Upon incorporation of DAG 1 in DPPC vesicles, formation of new isotropic phases was observed by P-31 NMR, These isotropic phases disappeared completely on opening the macrocyclic ring by a reducing agent. The thermotropic properties of DPPC bilayers having DAGs (1-6) incorporated at various concentrations were studied by differential scanning calorimetry. Incorporation of DAGs in general reduced the cooperativity unit (CU) of the vesicles. Similar experiments with reduced "open-chain" DAGs incorporated in a DPPC bilayer indicated a recovery of CU with respect to their macrocyclic "disulfide" counterparts. The effect of inclusion of these DAGs on the activity of phospholipase A(2) (PLA(2)) was studied in vitro. Incorporation of DAC 1 in DPPC membranes potentiated both bee venom and cobra venom PLA(2) activities.

The complementation of yeast with human or Plasmodium falciparum Hsp90 confers differential inhibitor sensitivities

Developing novel drugs against the unicellular parasite Plasmodium is complicated by the paucity of simple screening systems. Heat-shock proteins are an essential class of proteins for the parasite's cyclical life style between different cellular milieus and temperatures. The molecular chaperone Hsp90 assists a large variety of proteins, but its supporting functions for many proteins that are important for cancer have made it into a well-studied drug target. With a better understanding of the differences between Hsp90 of the malarial parasite and Hsp90 of its human host, new therapeutic options might become available. We have generated a set of isogenic strains of the budding yeast Saccharomyces cerevisiae where the essential yeast Hsp90 proteins have been replaced with either of the two human cytosolic isoforms Hsp90 alpha or Hsp90 beta, or with Hsp90 from Plasmodium falciparum (Pf). All strains express large amounts of the Flag-tagged Hsp90 proteins and are viable. Even though the strain with Pf Hsp90 grows more poorly, it provides a tool to reconstitute additional aspects of the parasite Hsp90 complex and its interactions with substrates in yeast as a living test tube. Upon exposure of the set of Hsp90 test strains to the two Hsp90 inhibitors radicicol (Rd) and geldanamycin (GA), we found that the strain with Pf Hsp90 is relatively more sensitive to GA than to Rd compared to the strains with human Hsp90's. This indicates that this set of yeast strains could be used to screen for new Pf Hsp90 inhibitors with a wider therapeutic window.

The effects of cholesterol inclusion on the vesicular membranes of cationic lipids

Small unilamellar vesicles formed from four cationic lipids in the absence and the presence of varying amounts of cholesterol were studied using fluorescence polarization and H-1-NMR techniques. The fluorescence polarization data clearly indicate that the packing order in the cationic lipid bilayers are affected by inclusion of cholesterol. importantly, this effect exists also with a cationic lipid that is devoid of any formal linkage region where the interaction of the lipid with cholesterol through hydrogen bonding is not feasible. The interactions of cholesterol with different types of cationic lipids in excess water have also been examined in multilamellar dispersions using proton magnetic resonance spectroscopy. In all the cases, the methylene proton linewidths in the NMR spectra respond to the addition of cholesterol to vesicles. Hydrophobic association of the lipid and cholesterol imposes restriction on the chain (CH2)(n) motions, leaving the terminal CH3 groups relatively mobile. On the basis of energy-minimized structural models, a rationale of the cholesterol-cationic lipid assembly has also been presented.

Oestrogenic regulation and differential expression of WNT4 in the bonnet monkey and rodent epididymis

A role for oestrogen in regulating fluid reabsorption in the monkey epididymis was recently demonstrated. Here, these Studies are extended to identify potential oestrogen-regulated proteins in the cauda region of monkey epididymis treated with vehicle and oestrogen receptor antagonist (ICI 182780). Two-dimensional electrophoretic analysis was used to identify the proteins. The results indicated down-regulation of WNT4 in the ICI-182780-treated monkey cauda. In addition. the Wnt4f mRNA concentration was also reduced in the caput regions of ICI-182780-treated rats and oestrogen receptor knockout mice. WNT4 is a key regulator of gonadal differentiation in humans and mice and plays a pivotal role in early mouse embryogenesis. The results of the present Study establish the presence of WNT4 in the monkey epididymis and its regulation by oestrogen, and Suggest a role for WNT4 in maintaining epididymal homeostasis.

Differential Games of Mixed Type with Control and Stopping Times

We study a zero sum differential game of mixed type where each player uses both control and stopping times. Under certain conditions we show that the value function for this problem exists and is the unique viscosity solution of the corresponding variational inequalities. We also show the existence of saddle point equilibrium for a special case of differential game.

Low-intensity differential photocapacitance of MOS structures

Some new observations on the phenomenon of photocapacitane on n-type silicon MOS structures under low intensities of illumination are reported. The difference between the illuminated and dark C---characteristics is automatically followed as a function of the applied bias thereby obtaining the differential photocapacitance and the resulting characteristics has been termed as the Low Intensity Differential Photocapacitance (LIDP). For an MOS capacitor, the LIDP characteristics is seen to go through a well defined maximum. The phenomenon has been investigated under different ambient conditions like light intensity, temperature, dependance of the frequency of the light etc. and it has been found that the phenomenon is due to a band excband excitation. In this connection, a novel sensitive technique for the measurement of the capacitance based upon following the frequency changes of a tank circuit is also described in some detail. It is also shown that the phenomenon can be understood by a simple theoretical model.

Structure-reactivity correlation in inclusion complexes: deoxycholic acid di-tert-butyl thioketone

Ultraviolet irradiation of crystalline molecular inclusion complexes of deoxycholic acid with di-tert-butyl thioketone results in no reaction. The structure of the above complex has been determined via X-ray diffraction. The absence of expected photoreactions. namely, photoreduction and photooxidation, is rationalized on the basis of the X-ray structure analysis of the complex.

Differential expression profiling of components associated with exoskeletal hardening in crustaceans

Background: Exoskeletal hardening in crustaceans can be attributed to mineralization and sclerotization of the organic matrix. Glycoproteins have been implicated in the calcification process of many matrices. Sclerotization, on the other hand, is catalysed by phenoloxidases, which also play a role in melanization and the immunological response in arthropods. Custom cDNA microarrays from Portunus pelagicus were used to identify genes possibly associated with the activation pathways involved in these processes. Results: Two genes potentially involved in the recognition of glycosylation, the C-type lectin receptor and the mannose-binding protein, were found to display molt cycle-related differential expression profiles. C-type lectin receptor up-regulation was found to coincide with periods associated with new uncalcified cuticle formation, while the up-regulation of mannose-binding protein occurred only in the post-molt stage, during which calcification takes place, implicating both in the regulation of calcification. Genes presumed to be involved in the phenoloxidase activation pathway that facilitates sclerotization also displayed molt cycle-related differential expression profiles. Members of the serine protease superfamily, trypsin-like and chymotrypsin-like, were up-regulated in the intermolt stage when compared to post-molt, while trypsin-like was also up-regulated in pre-molt compared to ecdysis. Additionally, up-regulation in pre- and intermolt stages was observed by transcripts encoding other phenoloxidase activators including the putative antibacterial protein carcinin-like, and clotting protein precursor-like. Furthermore, hemocyanin, itself with phenoloxidase activity, displayed an identical expression pattern to that of the phenoloxidase activators, i.e. up-regulation in pre- and intermolt. Conclusion: Cuticle hardening in crustaceans is a complex process that is precisely timed to occur in the post-molt stage of the molt cycle. We have identified differential expression patterns of several genes that are believed to be involved in biomineralization and sclerotization and propose possible regulatory mechanisms for these processes based on their expression profiles, such as the potential involvement of C-type lectin receptors and mannose binding protein in the regulation of calcification.

A multi-microprocessor architecture for solving partial differential equations

This paper presents the architecture of a fault-tolerant, special-purpose multi-microprocessor system for solving Partial Differential Equations (PDEs). The modular nature of the architecture allows the use of hundreds of Processing Elements (PEs) for high throughput. Its performance is evaluated by both analytical and simulation methods. The results indicate that the system can achieve high operation rates and is not sensitive to inter-processor communication delay.

Application of Haar functions for transmission line and transformer differential protection

The development of algorithms, based on Haar functions, for extracting the desired frequency components from transient power-system relaying signals is presented. The applications of these algorithms to impedance detection in transmission line protection and to harmonic restraint in transformer differential protection are discussed. For transmission line protection, three modes of application of the Haar algorithms are described: a full-cycle window algorithm, an approximate full-cycle window algorithm, and a half-cycle window algorithm. For power transformer differential protection, the combined second and fifth harmonic magnitude of the differential current is compared with that of fundamental to arrive at a trip decision. The proposed line protection algorithms are evaluated, under different fault conditions, using realistic relaying signals obtained from transient analysis conducted on a model 400 kV, 3-phase system. The transformer differential protection algorithms are also evaluated using a variety of simulated inrush and internal fault signals.

Sodium santalbate-dimethyl sulfate inclusion complex

A molecular inclusion complex has been obtained from the major acetylenic acid, santalbic acid (octadec-11-en-9-ynoic acid ortrans-11-octadecen-9-ynoic acid) of the seed oil ofSantalum album L. by a simple treatment of its sodium salt with dimethyl sulfate. Aqueous solutions (0.5–1%) of the complex produce good lather and have efficient cleansing (detergent) action on grease and dirt particles.

Mapping the integrity of differential obligations within the United Nations framework convention on climate change

This chapter unpacks public institutional integrity concepts through an examination of differential obligations within the global climate regime.

Screening of new lines of cereal grains for inclusion in Near Infra Red Scan calibrations

The project will provide enough data for a reliable and robust NIRs. It will more fully develop the in vitro method to enable less costly assessment of grains in the future. It will also provide a reliable assessment for DE which is the most expensive component of pig feed.

A Differential typing of Campylobacter

Establish a DNA-based typing scheme that allows the allocation of strains of Campylobacter to types that are host specific and/or non-host specific.