Converging lines of evidence implicate the beta-amyloid peptide (Ab) as causative in Alzheimer's disease. We describe a novel class of compounds that reduce Ab production by functionally inhibiting g-secretase, the activity responsible for the carboxy-terminal cleavage required for Ab production. These molecules are active in both 293 HEK cells and neuronal cultures, and exert their effect upon Ab production without affecting protein secretion, most notably in the secreted forms of the amyloid precursor protein (APP). Oral administration of one of these compounds, N-[N-(3,5-di¯uoro-phenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester, to mice transgenic for human APP V717F reduces brain levels of Ab in a dose-dependent manner within 3 h. These studies represent the ®rst demonstration of a reduction of brain Ab in vivo. Development of such novel functional g-secretase inhibitors will enable a clinical examination of the Ab hypothesis that Ab peptide drives the neuropathology observed in Alzheimer's disease.

Upon fertilization, drastic chromatin reorganization occurs during preimplantation development . However, the global chromatin landscape and its molecular dynamics in this period remain largely unexplored in humans. Here we investigate chromatin states in human preimplantation development using an improved assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) . We find widespread accessible chromatin regions in early human embryos that overlap extensively with putative cis-regulatory sequences and transposable elements. Integrative analyses show both conservation and divergence in regulatory circuitry between human and mouse early development, and between human pluripotency in vivo and human embryonic stem cells. In addition, we find widespread open chromatin regions before zygotic genome activation (ZGA). The accessible chromatin loci are readily found at CpG-rich promoters. Unexpectedly, many others reside in distal regions that overlap with DNA hypomethylated domains in human oocytes and are enriched for transcription factor-binding sites. A large portion of these regions then become inaccessible after ZGA in a transcription-dependent manner. Notably, such extensive chromatin reorganization during ZGA is conserved in mice and correlates with the reprogramming of the non-canonical histone mark H3K4me3, which is uniquely linked to genome silencing. Taken together, these data not only reveal a conserved principle that underlies the chromatin transition during mammalian ZGA, but also help to advance our understanding of epigenetic reprogramming during human early development and in vitro fertilization.

Time-of-flight mass spectrometry (TOFMS) is coupled online with capillary electrophoresis (CE) to analyze mixtures of biomolecules using an electrospray ionization (ESI) interface. The eluent is electrosprayed directly from the CE capillary

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We describe the development of statine-based peptidomimetic inhibitors of human beta-secretase (BACE). The conversion of the peptide inhibitor 1 into cell-permeable peptidomimetic inhibitors of BACE was achieved through an iterative strategy of conceptually subdividing 1 into three regions: an N-terminal portion, a central statine-containing core, and a C-terminus. Replacement of the amino acid residues of 1 with moieties with less peptidic character was done with retention of BACE enzyme inhibitory activity. This approach led to the identification of the cell-permeable BACE inhibitor 38 that demonstrated BACE-mechanism-selective inhibition of Abeta secretion in human embryonic kidney cells.

The hydroxyethylene (HE) transition state isostere was developed as a scaffold to provide potent, small molecule inhibitors of human beta-secretase (BACE). The previous work on the statine series proved critical to the discovery of HE structure-activity relationships. Compound 20 with the N-terminal isophthalamide proved to be the most potent HE inhibitor (IC(50) = 30 nM) toward BACE. Unlike the statine series, we identified HE inhibitors without carboxylic acids on the C terminus, leading to enhanced cell penetration and making them attractive candidates for further drug development in Alzheimer's disease.

The quality of combinatorial libraries determines the success of biological screening in drug discovery programs. In this paper, we evaluate and compare various methods for measuring identity, purity, and quantity (yield) of combinatorial libraries. Determination of quantitative purity reveals the true library quality and often indicates potential quality problems before full-scale library production. The relative purity can be determined for every member in a large library in a high-throughput mode, but must be cautiously interpreted. In particular, many impurities are not observable by relative purity measurements using detectors such as UV(214), UV(254), and evaporative light-scattering detection. These "invisible" impurities may constitute a significant portion of the sample weight. We found that TFA, plastic extracts, inorganic compounds, and resin washout are among these impurities. With compelling evidence, we reach a conclusion that purification is the only way to remove "invisible" impurities and improve the quantitative purity of any compound even though some compounds may have a high relative purity before purification.

Four methods, including voltammetric measurement of double layer capacitance, surface oxides reduction, under potential deposition of Cu and carbon monoxide (CO) stripping have been applied to evaluate the real surface area of a polycrystalline Pd (pc-Pd) electrode. The results reveal that the second and third methods lead to consistent results with deviations below 5%. And from the determined double layer capacitance and CO stripping charge, it is deduced that the double layer capacity unit area is 23.1±0.4 μF/cm2 and the saturated CO adlayer should be ca. 0.66 ML in order to ensure that the real surface area as determined is consistent with the other two techniques. The applicability as well as the attentions when applying these techniques for the determination of the real surface area of pc-Pd electrodes have been discussed.