Solar neutrino problem in light of super-Kamiokande data

I discuss the status of the accepted solutions to the solar neutrino problem in light of the super-Kamiokande data.     

pH‐Triggered Sustained Drug Delivery from a Polymer Micelle having the β‐Thiopropionate Linkage

The synthesis, micellar aggregation, and pH‐triggered intracellular drug delivery ability of an amphiphilic statistical copolymer (P2) are studied. Two methacrylate derivatives, one containing a hydrophilic pendant and the other containing a hydrophobic pendant chain, are copolymerized to produce P2. The hydrophobic pendant chain is linked to the polymer backbone by a β‐thiopropionate linkage, known to undergo slow hydrolysis at mild acidic pH. P2 forms a multimicellar cluster in water with a critical aggregation concentration of 0.02 mg mL⁻¹ and encapsulates a hydrophobic guest such as pyrene, Nile red, or the anti‐cancer drug doxorubicin (Dox). Sustained release of the entrapped Dox (80% after 100 h) is noticed at pH 5.2, while release is significantly slower (35% after 100 h) at pH 7.4. Acidic hydrolysis of the β‐thiopropionate linkage leading to the reduction of the hydrophobicity is established as the cause for micellar disassembly and triggered drug release. Cell‐culture studies with the human breast cancer cell line, MCF‐7, reveal biocompatibility of P2 (below 150 μg mL⁻¹). It is further tested for intracellular delivery of Dox. MCF‐7 cells remain healthy at pH 7.4 but become unhealthy at pH 5.2 when treated with a Dox‐loaded P2 micelles.

     

Green fluorescent protein-expressing Escherichia coli as a model system for investigating the antimicrobial activities of silver nanoparticles

Recombinant Escherichia coli (E. coli) bacteria expressing green fluorescent protein (GFP) was used as a model system to investigate the antimicrobial activities of Ag nanoparticles (NPs). A convenient in situ method of Ag NP synthesis using sodium borohydride, in the bacterial growth medium, was developed to produce preformed NPs for the study. Fluorescence spectroscopic and microscopic techniques allowed rapid detection of time-dependent changes in bacterial growth as well as fluorescence characteristics in the presence of Ag NPs. In addition, X-ray diffraction, UV-vis spectroscopic, and transmission electron microscopic measurements were carried out to understand the effect of Ag NPs on the bacteria. Our observations indicated that Ag NPs, above a certain concentration, not only were bactericidal but also were found to reduce the sizes of treated bacteria in comparison to untreated ones. Cell lysis of Ag NP-treated bacteria was suggested by the increased GFP fluorescence obtained in the medium. In vitro DNA-Ag NP interaction was detected by spectrophotometric analysis. However, electrophoresis studies indicated no direct effect of Ag NPs on DNA or protein profiles.     

Aminohydroxyphosphine ligand for the copper-catalyzed enantioselective conjugate addition of organozinc reagents

An alanine-derived aminohydroxyphosphine ligand was developed for copper-catalyzed asymmetric conjugate addition of organozinc reagents to alpha,beta-unsaturated carbonyl compounds. This new tridentate ligand induces consistently high enantioselectivity in reactions of a variety of acyclic substrates. Theoretical mechanistic analysis suggests that the C-C bond formation takes place through a highly ordered transition state by the coordination of the phosphorus and nitrogen atoms to the copper(III) and zinc(II) atoms, respectively, and of the oxygen anion to both the metal centers.     

How do women decide? Accepting or declining BRCA1/2 testing in a nationwide clinical sample in the United States

OBJECTIVE: To examine the role of the practitioner, informed consent, and genetic counseling in genetic testing decisions and to assess their relative influence on women's decision to have clinical BRCA1/2 testing. METHODS: Qualitative study using in-depth open-ended interviews with 68 women who had considered clinical BRCA1/2 testing. RESULTS: Slightly less than half of the women who had considered BRCA1/2 testing were found to have had a clear and preexisting desire to test or not to test, irrespective of practitioner attitude or advice. CONCLUSION: The decision to accept or decline genetic testing is the result of a complex process that goes beyond interactions between health care providers and patients, indicating a caution against exclusive reliance on informed consent or counseling encounters.     

A remarkably bent diiron(III)-μ-hydroxo bisporphyrin: unusual stabilization of two spin states of iron in a single molecular framework

A novel diiron(III) bisporphyrin bridged by a hydroxo group between two cofacial Fe centers is reported. X-ray structural characterization revealed the remarkably bent μ-hydroxobis[Fe(III) porphyrin] with the smallest known Fe-O(H)-Fe angle [142.5(2)°] reported to date in an iron porphyrin. The close approach of the two rings in the molecule results in an unequal core deformation, and as a result, the geometrical parameters (such as the Fe-N(p), Fe-O and Fe···Ct(p) distances) are all different for the two Fe(III) centers, leading for the first time to a natural way of stabilizing two different spins of iron in a single molecular framework with complete retention of their own spectroscopic identities in both the solid state and solution. The strong antiferromagnetic coupling between the two Fe(III) centers in the μ-oxo dimer (-J = 126.6 cm(-1)) is attenuated to only 4.5 cm(-1) simply by protonation to give the μ-hydroxo complex.