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Matrix metalloproteases (MMPs) play an important role in cartilage homeostasis under both normal and inflamed disease states and, thus, have become attractive targets for the treatment of arthritic diseases. Herein, we describe the identification of a potent, selective MMP-13 inhibitor, developed using fragment-based structure-guided lead identification and optimization techniques. Virtual screening methods identified a novel, indole-based MMP-13 inhibitor that bound into the S1' pocket of the protein exhibiting a novel interaction pattern hitherto not observed in MMP-13 inhibitors. X-ray crystallographic structures were used to guide the elaboration of the fragment, ultimately leading to a potent inhibitor that was >100-fold selective over nine other MMP isoforms tested.

A new and very direct enantioselective total synthesis of members of the β-amyrin family of pentacyclic triterpenes has been developed starting with acylsilane 5, 2-propenyllithium, and cyclohexenylmethyl bromide 6, which were assembled to form tetraene 7. Cationic cyclization of 7 and silylation afforded 8, which after vinyl triflate formation was cyclized via a Cu(I) intermediate (Scheme ) to form the TBS ether of aegiceradienol 10, a versatile intermediate that is readily converted into natural β-amyrins such as β-amyrin (1) and oleanolic acid (2). The C(14)-diastereomer (13) of aegiceradienol was also synthesized from the C(14)-diastereomer of 8 using an intramolecular Stille reaction for the closure of ring D (Scheme ).

Based on the Mie scattering theory, we study optical resonances with whispering gallery modes (WGMs) in tubular microcavities. Rigorous formulas are present to obtain resonant wavelengths and Q factors for the WGM resonances. It is found that the Q factors of microtubes can be dramatically increased by increasing the dielectric constants in tube walls. For common SiO/SiO2 based microtubes, Q factors can be improved by one order when the microtubes are coated with thin high-index HfO2 layers (n = 1.95, thickness = 10 nm). The results could be useful for designing better optical devices based on tubular microcavities.

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We numerically study the optical absorption in Si nanowire and nanoporous Si structures that have potential applications in solar cells. It is found that for the same thickness and filling ratio of Si, thin nanoporous structures can have much higher absorption than thin Si nanowire arrays. Above a critical filling ratio of Si (0.25), the nanoporous structures can have higher absorption even than thin films with the same thickness. For solar cells based on thin nanoporous Si structures, the maximal ultimate efficiency occurs when the filling ratio is around 0.3.

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