Antibody recognition of chiral surfaces. Enantiomorphous crystals of leucine-leucine-tyrosine

Monoclonal antibodies were selected after immunization with crystals of the tripeptide l-leucine-l-leucine-l-tyrosine. They interact with the tripeptide crystals, but do not interact with the tripeptide molecule, with other crystalline surfaces, or with adsorbed protein. The interactions of two antibodies with crystals of l-Leu-l-Leu-l-Tyr and of its enantiomer d-Leu-d-Leu-d-Tyr were characterized in depth. Antibody 48E is stereoselective and enantioselective: it recognizes only the [011] faces of the l-Leu-l-Leu-l-Tyr crystals, and not the enantiomorphous [011] faces of d-Leu-d-Leu-d-Tyr crystals, or any other faces of either crystal. In contrast, antibody 602E is poorly stereoselective and is not enantioselective: it recognizes the crystals of both enantiomers, interacting with a number of different faces of each. The different recognition patterns are explained on the basis of the nature of the interactions and the structure of the interacting surfaces. Understanding this antibody specificity advances our general understanding of surface recognition and transfer of chiral information across biological interfaces.     

Giant Vortex and the Breakdown of Strong Pinning in a Rotating Bose-Einstein Condensate

We consider a two-dimensional model for a rotating Bose-Einstein condensate (BEC) in an anharmonic trap. The special shape of the trapping potential, negative in a central hole and positive in an annulus, favors an annular shape for the support of the wave function u. We study the minimizers of the energy in the Thomas-Fermi limit, where a small parameter ɛ tends to 0, for two different regimes of the rotational speed Ω. When Ω is independent of ɛ, we observe that the energy minimizers acquire vorticity beyond a critical Ω, but the vortices are strongly pinned in the central hole where the potential is negative. In this regime, minimizers exhibit no vortices in the annular bulk of the condensate. There is a critical rotational speed Ω=O(|lnɛ|) for which this strong pinning effect breaks down and vortices begin to appear in the annular bulk. We derive an asymptotic formula for the critical Ω, and determine precisely the location of nucleation of the vortices at the critical value. These results are related to very recent experimental and numerical observations on BEC.     

Interpenetrating Networks Obtained by Crosslinking in the Vinylacetate (VAc)-Triethoxyvinylsilane (VTES)-Tetraethoxysilane (TEOS) System

In the present work the sol-gel process in the ternary system VAc-VTES-TEOS was approached. The monomer that ensures the crosslinking of the obtained networks is VTES, which could react with VAc by free-radical polymerisation and with TEOS by hydrolysis-polycondensation. The early stage evolution of the process was monitored by gas chromatography coupled with mass spectrometry (GC-MS). The gels obtained were characterised by IR spectroscopy, DTA/TG analysis and DSC measurements. Important differences in the gelling process and in the properties of the obtained gels could be noticed, related to the presence of VAc and VTES in the reaction mixtures. The investigation allowed to establish the compositions and the experimental conditions in which gels with high degree of crosslinking could be obtained.     

SELECTIVE PHOTOSENSITIZED OXIDATION OF THE METHIONYL RESIDUES IN ELASTASE

In recent years, significant advances have clarified the mechanism of photosensitized oxidations (see, for example, Foote, 1968), especially as regards the nature of the reactive oxidizing agents. This fact stimulated the development of reaction systems which allow selective photooxidation of specific components of biological macromolecules (Spikes and Livingston, 1969; Spikes and MacKnight, 1970). In the field of proteins, the selective conversion of the methionyl residues to the sulfoxide can be achieved by irradiation with visible light in the presence of hematoporphyrin at neutral or acid pH (Jori et al. , 1969).     

Photophysical properties and antibacterial activity of meso-substituted cationic porphyrins

A series of derivatives of 5,10,15,20-tetrakis-(4-N-methylpyridyl)-porphine, where one N-methyl group was replaced by a hydrocarbon chain ranging from C6 to C22, were characterized for their photophysical and photosensitizing properties. The absorption and fluorescence features of the various compounds in neutral aqueous solutions were typical of largely monomeric porphyrins, with the exception of the C22 derivative, which appeared to be extensively aggregated. This was confirmed by the very low triplet quantum yield and lifetime of the C22 derivative as compared with 0.2-0.7 quantum yields and 88-167 micros lifetimes for the other porphyrins. The photophysical properties and photosensitizing activity toward N-acetyl-L-tryptophanamide of the C22 porphyrin became comparable to those typical of the other derivatives in 2% aqueous sodium dodecyl sulfate, where the C22 compound is fully monomerized. All the porphyrin derivatives exhibited at micromolar concentrations photoinactivation activity against both Staphylococcus aureus and Escherichia coli, even though the gram-negative bacteria were markedly less photosensitive. The photosensitizing efficiency was influenced by (1) the amount of cell-bound porphyrin, which increased with increasing length of the hydrocarbon chain; and (2) the tendency to undergo partial aggregation in the cell, which seems to be especially important for the C22 derivative.     

Photofrin as a specific radiosensitizing agent for tumors: studies in comparison to other porphyrins, in an experimental in vivo model

The use of ionizing radiation for tumor treatment represents a well established therapeutic modality. The efficiency and selectivity of radiotherapeutic protocols can be often enhanced by the addition of specific chemical compounds that optimise the response of the tumor to the incident radiation as compared with peritumoral tissue districts. The results of this study showed that Photofrin, a porphyrin derivative which is presently used as a tumor-photosensitizing agent in photodynamic therapy (PDT), can also act as an efficient tumor radiosensitizer. To test this possibility, we used nude mice subcutaneously implanted with human bladder cancer RT4. The mice were injected with different porphyrin-type photosensitizing agents, including Photofrin, 5-aminolevulinic acid, chlorin e(6), haematoporphyrin, protoporphyrin, Zn-tetrasulphophtalocyanine, and irradiated with 5 and 15 Gy using a Siemens X-ray device. Even though all the porphyrins accumulated in significant amounts in the neoplastic lesion, only Photofrin significantly improved the response of the tumor to irradiation by increasing the doubling time of the tumor volume from 6.2 days in the untreated control group to 10.9 days in the 5 and 15 Gy-irradiated groups. The tumor response was maximal with injected Photofrin doses of 7.5 mg/kg, and was not further enhanced by injection of higher doses. Our hypothesis is, that the radiosensitizing effect of Photofrin seems to be due to some oligomeric constituents which could specifically react with radiogenerated-radicals thereby amplifying the effect of the X-ray radiation.     

Selective removal of nitrate by using a novel macroporous acrylic anion exchange resin

An anion exchange resin NDP-5 has been prepared successfully and applied on the selective removal of nitrate from SO₄^2-/ NO₃^- binary co-existence system.The composition and morphology of NDP-5 were confirmed by FT-IR and SEM.The NDP-5 resin exhibits the completely different behavior on the adsorption capacity,adsorption kinetic and the effect of the completing anion in the absence or presence of sulfate,compared to D213.And,the resultants of kinetic are well fitted by the pseudo-first-order and pseudo-second-order models.These results are very important to develop novel resins with great features.     

Thermal,chemical, biological and mechanical properties of chitosan films with powder of eggshell membrane for biomedical applications

Journal of Thermal Analysis and Calorimetry - The objective of this work was to develop chitosan films incorporated with the eggshell membrane powder (MCO) by the solvent evaporation method with...     

Syntheses of 5′‐Nucleoside Monophosphate Derivatives with Unique Aminal,Hemiaminal, and Hemithioaminal Functionalities: A New Class of 5′‐Peptidyl Nucleotides

A number of synthetically useful transformations have been developed to generate novel 5′‐peptidyl nucleoside monophosphate analogues that incorporate sensitive phosphoaminal, ‐hemiaminal or ‐hemithioaminal functionalities. The strategies adopted entailed the coupling between dipeptides, which enclose a reactive Cα‐functionalized glycine residue and phosphate or phosphorothioate moieties. These developments led to potentially powerful and general methodologies for the preparation of α‐phosphorylated pseudopeptides as well as nucleoside monophosphate mimics. The resulting conjugates are of interest for a variety of important applications, which range from drug development to synthetic biology, as pronucleotides or artificial building blocks for the enzymatic synthesis of xenobiotic information systems. The potential of all dipeptide‐TMP conjugates as pyrophosphate mimics in the DNA polymerization reaction was tested, and the influence of the nature of the linker was evaluated by in vitro chain elongation assay in the presence of wild‐type microbial DNA polymerases.