UVB Shielding Role of FeCI3 and Certain Cyanobacterial Pigments

The shielding role of ferric iron (FeCl₃) and certain cyanobacterial pigments (a brown-colored pigment from Scytonema hofmanii culture filtrate and a pink extract from Nostoc spongiaeforme) against UVB-induced damage in the filamentous, nitrogen-fixing cyanobacterium Nostoc muscorum has been demonstrated. Addition of these colored compounds to agarose gels (1–3 mm thick) resulted in a considerable decrease in UVB transmittance through the gels. The lowest UVB transmittance (15%) occurred through a 3 mm gel containing 0.01% FeCl₃ followed by S. hofmanii culture filtrate (40%) and N. spongiaeforme extract (50%). These substances appear to act as very efficient UVB-absorbing screens. Percent survival and ¹⁴CO₂ uptake of N. muscorum increased significantly if UVB exposure was given on gels containing FeCl₃ or other UVB-shielding substances. The highest protection of N. muscorum was recorded with FeCl₃, followed by S. hofmanii culture filtrate and N. spongiaeforme extract. Such UV-shielding substances if present in required concentration range may enhance the survival of cyanobacteria exposed to high levels of UVB.     

Highly efficient diastereoselective biocatalytic acylation of a diastereotopic furanose diol and synthesis of key intermediates for amino derivatized bicyclonucleosides

The selectivity of Candida antarctica lipase has been demonstrated and employed in the manipulation of a diastereotopic furanose diol as the key step in the synthesis of a novel bicyclo 3-amino-3-deoxy furanose derivative, which is an important intermediate for the synthesis of bicyclic analogs of AZT. The asymmetrization of the diol has been achieved with preferred formation of a monoacylated product with 100% diastereoselectivity. An efficient synthesis of an intermediate in the synthesis of amino derivatized bicyclonucleosides is also described, two such novel compounds containing cycloamino residues have been prepared.     

Chromatographic separation of strontium from barites for mass spectrometric analysis

Summary A simple Chromatographic method for the separation of strontium in barites containing 500 times excess barium is described. The strontium fraction is sufficiently pure for mass spectrometer studies of strontiumisotopes. The resin used is Dowex-50 and the column dimensions are 1.1 by 8 cm. The column is eluted at room temperature with 1.5M hydrochloric acid at a flow rate of 1 ml/min. Effect of column temperature on the elution peaks is pointed out.

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Zusammenfassung Eine einfache chromatographische Methode zur Abtrennung von Strontium, aus Baryten mit 500fachem Bariumüberschuß wurde angegeben. Die Strontiumfraktion ist genügend rein für massenspektrometrische Untersuchungen der Sr-Isotopen. Dowex-50 dient als Austauscher in 1,1×8-cm-Säulen. Die Elution erfolgt bei Zimmertemperatur mit 1,5-m Salzsäure bei einer Durchflußgeschwindigkeit von etwa 1 ml/min. Der Einfluß der Säulentemperatur auf die Elutionspeaks wird hervorgehoben.

     

An affinity probe for isolation of abscisic acid-binding proteins

An affinity probe has been developed for isolation of receptor proteins that bind the plant hormone abscisic acid (ABA). The structural features required for biological activity have been preserved, and the probe has been demonstrated to bind to known ABA-binding proteins.     

The interplay of secondary Te?N, Te?O, Te?I and I?I interactions, Te?π contacts and π-stacking in the supramolecular structures of [{2-(4-nitrobenzylideneamino)-5-methyl}phenyl](4-methoxyphenyl)tellurium dihalides

The unsymmetrically substituted diorganotellurium dihalides [2-(4,4′-NO₂C₆H₄CHNC₆H₃Me]RTeX₂ (R = 4-MeOC₆H₄, X = Cl, 1a; Br, 1b; I, 1c; R = 4-MeC₆H₄; X = Cl, 2; R = C₆H₅, X = Cl, 3) were prepared in good yields and characterized by solution and solid-state ¹²⁵Te NMR spectroscopy, IR spectroscopy and X-ray crystallography. In the solid-state, molecular structures of 1a and 1c possess scarcely observed 1,4-type intramolecular Te?N secondary interaction. Crystal packing of these compounds show an unusually rich diversity of intermolecular secondary, Te?O, Te?I and I?I interactions, Te?π contacts as well as extensive π-stacking of the organic substituents.     

(La0.4Ba0.4Ca0.2)(Mn0.4Ti0.6)O3: A new titano-manganate with a high dielectric constant and antiferromagnetic interactions

A new perovskite-based titano-manganate, (La_0.4Ba_0.4Ca_0.2)(Mn_0.4Ti_0.6)O₃, has been prepared by the ceramic route at 1100°C. This oxide was found to possess the cubic perovskite structure with  Å (space group ). The refined composition as obtained by Rietveld analysis of powder X-ray data was found to be (La_0.44Ba_0.38Ca_0.18)(Mn_0.43Ti_0.57)O_2.91(3) (R_p=0.0704, wR_p=0.0828). The composition was also ascertained by Energy dispersive X-ray analysis. Iodometric studies led to a slightly higher oxygen content (compared to Rietveld refinement) corresponding to an average manganese oxidation state of 3.05. The above oxide was found to exhibit high dielectric constant (ε) of 6980 at 1 kHz decreasing to 590 at 100 kHz. At high temperatures (200°C) it shows an unusually high dielectric constant of 20,000 at 1 kHz. In addition to the dielectric properties, detailed magnetic studies show evidence of long-range antiferromagnetic interactions near 5 K. The presence of unusually high dielectric constant coupled with the long-range magnetic interactions may open up interesting applications.     

A note on the torsional potential functionV(φ) in the dipeptide model

The studies made on N-methyl acetamide (NMA), N-ethyl acetamide (NEA), N-isopropyl acetamide (NIA), using semi-empirical quantum chemical methods have indicated that NMA is not the proper model compound for arriving at the form ofV(φ), whereas NEA and NIA molecules are suggested as model systems for arriving at the form of the potential functionV(φ). The present calculations have indicated thatV(φ) is of the form 1/2 and not (1 — cos3φ); however the value of barrier heightV(φ) was found to be very small. So it is suggested that there is no need of separately adding theV(φ) term in empirical potential energy calculations.     

Constrained anisotropic dipole oscillator strength distribution techniques,and reliable results for anisotropic and isotropic dipole molecular properties,with applications to H2 and N2

Summary Constrained anisotropic dipole oscillator strength distribution techniques are discussed and applied to obtain reliable results for a wide variety of the anisotropic and isotropic dipole properties of H₂ and N₂. These include the dipole oscillator strength sumsS _k, k=2, 1, –1/2(–1/2) –2, –3, –4, ..., the logarithmic dipole sumsL _k and mean excitation energiesI _k, k=2(–1) – 2, and, as a function of wavelength, the dynamic polarizability and the associated anisotropy, the total depolarization ratio, the Rayleigh scattering cross section, and the Verdet constant. The anisotropic components of the DOSD for a molecule are obtained from a given recommended isotropic DOSD by using a constrained least squares procedure and a series of known anisotropic constraints. Assuming that sufficient input is available, the constrained DOSD approach used in this paper is the only available method for the reliable evaluation ofall the relevant anisotropic and isotropic dipole properties for a wide variety of atoms and molecules.This research was supported by a grant from the Natural Sciences and Engineering Research Council of CanadaOn leave from Department of Physics, Meerut University, Meerut, India     

Factors Affecting Extracellular Vesicles Based Drug Delivery Systems

Extracellular vesicles (EVs) play major roles in intracellular communication and participate in several biological functions in both normal and pathological conditions. Surface modification of EVs via various ligands, such as proteins, peptides, or aptamers, offers great potential as a means to achieve targeted delivery of therapeutic cargo, i.e., in drug delivery systems (DDS). This review summarizes recent studies pertaining to the development of EV-based DDS and its advantages compared to conventional nano drug delivery systems (NDDS). First, we compare liposomes and exosomes in terms of their distinct benefits in DDS. Second, we analyze what to consider for achieving better isolation, yield, and characterization of EVs for DDS. Third, we summarize different methods for the modification of surface of EVs, followed by discussion about different origins of EVs and their role in developing DDS. Next, several major methods for encapsulating therapeutic cargos in EVs have been summarized. Finally, we discuss key challenges and pose important open questions which warrant further investigation to develop more effective EV-based DDS.