A recently developed spectroscopic technique was used to determine oxygen diffusion coefficients, D, as a function of temperature in polystyrene and polycarbonate films. The data were quantified by using an Arrhenius expression with the following variables: (a) a diffusion activation barrier, Eact, and (b) a diffusion coefficient, D0, that represents the condition of "barrier-free" gas transport. From the perspective that diffusion depends on free volume, the parameters £act and Do are interpreted to reflect dynamic and static elements of free volume in the polymer matrix. The addition of low molecular weight solutes to these amorphous glasses can alter the oxygen diffusion coefficient by affecting the dynamic and/or static free volume of the material. These effects are manifested in the parameters £act and Do. Depending on the temperature, the additive may either inhibit or facilitate oxygen diffusion relative to diffusion in the unperturbed, additivefree material. Data are reported for films containing dimethyl phthalate, diphenyl phthalate, cholestane, and molecular nitrogen as additives.

Several miRNAs have recently been identified to regulate adipocyte or osteoblast differentiation or both. In this study, miR-223 was found to be involved in the reciprocal regulation of adipocyte and osteoblast differentiation. miR-223 was induced in primary cultured mouse marrow stromal cell, mesenchymal line C3H10T1/2 and stromal line ST2 after adipogenic treatment. Conversely, it was reduced in preosteoblast MC3T3-E1 after osteogenic treatment. Supplementing miR-223 levels using synthetic miR-223 mimics significantly suppressed the growth of the C3H10T1/2 and ST2 cells and induced the progenitor cells to fully differentiate into adipocytes, along with induction of adipocyte-specific transcription factors peroxisome proliferator-activated receptor c, CCAAT/enhancer binding protein-a (C/EBPa), and marker genes aP2 and adipsin. By contrast, depletion of the endogenous miR-223 using synthetic miR-223 inhibitor repressed the progenitor cells to differentiate. The effects of miR-223 on adipocyte formation from ST2 cells were also demonstrated by using lentivirus that overexpresses miR-223. Conversely, supplementing miR-223 blocked ST2 to differentiate into osteoblasts. Fibroblast growth factor receptor 2 (Fgfr2), a critical regulator of osteoblast, was shown to be a direct target of miR-223 by using dual luciferase reporter assay. Knockdown of Fgfr2 in C3H10T1/2 downregulated phosphorylation of ERK1/2 and upregulated expression of C/EBPa and dramatically enhanced the differentiation of the cells into adipocytes. Further investigation of mechanisms that control miR-223 expression demonstrated that C/EBPs induced miR-223 expression through binding to the promoter regions of the miR-223. Taken together, our study provides evidences that miR-223 regulates adipocyte and osteoblast differentiation through a novel C/EBPs/miR-223/FGFR2 regulatory feedback loop. STEM CELLS 2015;33:1589-1600

A high incidence of sensitization to Blomia tropicalis, the predominant house dust mite species in tropical regions, is strongly associated with allergic diseases in Singapore, Malaysia, and Brazil. IgE binding to the group 5 allergen, Blo t 5, is found to be the most prevalent among all B. tropicalis allergens. The NMR structure of Blo t 5 determined represents a novel helical bundle structure consisting of three antiparallel α-helices. Based on the structure and sequence alignment with other known group 5 dust mite allergens, surface-exposed charged residues have been identified for site-directed mutagenesis and IgE binding assays. Four charged residues, Glu76, Asp81, Glu86, and Glu91 at around the turn region connecting helices α2 and α3 have been identified to be involved in the IgE binding. Using overlapping peptides, we have confirmed that these charged residues are located on a major putative linear IgE epitope of Blo t 5 from residues 76–91 comprising the sequence ELKRTDLNILERFNYE. Triple and quadruple mutants have been generated and found to exhibit significantly lower IgE binding and reduced responses in skin prick tests. The mutants induced similar PBMC proliferation as the wild-type protein but with reduced Th2:Th1 cytokines ratio. Mass screening on a quadruple mutant showed a 40% reduction in IgE binding in 35 of 42 sera of atopic individuals. Findings in this study further stressed the importance of surface-charged residues on IgE binding and have implications in the cross-reactivity and use of Blo t 5 mutants as a hypoallergen for immunotherapy.

The three-dimensional structures of indinavir and three newly synthesized indinavir analogs in complex with a multi-drug-resistant variant (L63P, V82T, I84V) of HIV-1 protease were determined to ∼2.2 Å resolution. Two of the three analogs have only a single modification of indinavir, and their binding affinities to the variant HIV-1 protease are enhanced over that of indinavir. However, when both modifications were combined into a single compound, the binding affinity to the protease variant was reduced. On close examination, the structural rearrangements in the protease that occur in the tightest binding inhibitor complex are mutually exclusive with the structural rearrangements seen in the second tightest inhibitor complex. This occurs as adaptations in the S1 pocket of one monomer propagate through the dimer and affect the conformation of the S1 loop near P81 of the other monomer. Therefore, structural rearrangements that occur within the protease when it binds to an inhibitor with a single modification must be accounted for in the design of inhibitors with multiple modifications. This consideration is necessary to develop inhibitors that bind sufficiently tightly to drug-resistant variants of HIV-1 protease to potentially become the next generation of therapeutic agents.

Diffusion coefficients for oxygen in polymer films are quickly and accurately obtained by using a near-infrared luminescence spectrometer. The spectroscopic technique described herein uses the 1270-nm phosphorescence of singlet molecular oxygen ('AgOa -* 32g~02) to directly monitor oxygen sorption into polymer films (15-80 pm thick) of small area (~1 cm X 1 cm). The approach is illustrated by using films of polystyrene for which a 25 °C diffusion coefficient of (2.3 ± 0.3) X 10'7 cm2/s is obtained.