The crystal structure of the complex formed by bovine trypsin and Bowman-Birk type protease inhibitor AB-I extracted from azuki beans (Vigna angularis) 'Takara' has been analyzed. The structure was solved by the application of the phase combination of single isomorphous phases and trypsin model phases, followed by phase improvement using the iterative Fourier technique. From the resulting electron density map, a three-dimensional atomic model of the trypsin binding domain of AB-I has been built. The peptide chain at the trypsin reactive site turns back sharply at Pro29 and forms a 9-residue ring (Cys24-Cys32). The 'front side' of this ring, consisting of the reactive site (Cys24-Met28), interacts with trypsin in a similar manner to other families of inhibitors and forms a stable complex, which seems to be maintained by the interactions with the 'back side' of this ring (Pro29-Cys34). The similar spatial arrangements of the 'back side' of this inhibitor and the 'secondary contact region' of the other inhibitors with respect to the reactive site suggest an important common role of these regions in exhibiting inhibitory activity.

Novel molybdenum-and tungsten-based catalysts induced stereospecific ring-opening metathesis polymerization (ROMP) of cycloolefins to produce a new class of crystalline polymers. Various monomeric molybdenum(VI) and tungsten(VI) complexes of the general formula M()O)(O-Ar) 4 (M ) Mo or W;(O-Ar)4 is two biphenolate or four phenolate ligands) were prepared. These catalysts exhibited moderate ROMP activity in the presence of cocatalyst such as n-BuLi and Et3Al. The molybdenum and tungsten complexes bearing substituted biphenolate ligands such as oxomolybdenum(VI) bis(racemic-5,5′,6,6′-tertamethyl-3,3′-di-tert-butyl-1,1′-biphenyl-2,2′-diolate) promoted cis and isospecific ROMP of endodicyclopentadiene (cis > 90% and meso > 95%). The novel ternary and quarternary catalysts such as MoOCl 4-biphenolate-n-BuLi (1:2:2) were developed as a new useful methodology to control the stereoselectivity of the ROMP. Hydrogenation of the cis-isotactic poly(endo-dicyclopentadiene)s and poly-(norbornene)s provided novel crystalline polymers with high melting points (295 °C, ∆H ) 50 J/g; 175 °C, ∆H ) 60 J/g, respectively), which can be regarded as a new class of crystalline polymers.

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Crystalline styrene-butadiene-styrene (SBS) triblock copolymers consisting of elastic cispolybutadiene (cis-PB) chemically bonded with crystallizable syndiotactic polystyrene (syn-PS) were synthesized through a stereospecific sequential triblock copolymerization of S with B catalyzed by C 5 Me 5 TiMe 3 /B(C 6 F 5 ) 3 / trioctylaluminum (Al(oct) 3 ) under controllable polymerization conditions. The first polymerization step was conducted at -25 °C, yielding syn-PS with controllable molecular weight by changing the polymerization time.The second one was started with the addition of excess B to the progressing syn-PS polymerization at -40 °C, yielding syn-PS/cis-PB diblock copolymer with high block efficiencies. The third one was conducted at -25 °C just by removal of the unreacted B in order to enhance the reinsertion and propagation of the remained S, yielding crystalline SBS triblock copolymers with relatively high PS compositions. The livingness of the whole polymerization process was confirmed through a linear increase of the molecular weights of the polymer products obtained in each step against their polymer yields, while keeping the polydispersity values almost constant. The 13 C NMR analysis of the copolymer product proves that the PS blocks were highly syndiotactic ([rrrr] > 95%), and the PB block was primarily cis-1,4 structure (>70%). Cross-fractionation chromatography (CFC) was used to evaluate the contamination of the dead polymers in the crystalline SBS. Transmission electronic microscopy (TEM) was used to observe the phased separation morphology of the PS and PB blocks in the crystalline SBS. The existence of the syn-PS blocks in the crystalline SBS was further confirmed with the observation of a strong endothermic peak at 272 °C in their differential scanning calorimetry (DSC) curves. Preliminary results on the heat deformation stability as well as the chemical resistance property of this new material have also been evaluated in comparison with those of the corresponding anionic SBS materials.

Properties of the tactic and atactic hydrogenated ring-opened poly(endo-dicyclopentadiene)s and features of the tungsten imido/phenolate-catalyzed stereoselective ring-opening metathesis polymerizations (ROMP) were studied. Several tungsten(VI) imido phenolate complexes were synthesized and exhibited moderate ROMP activity in the presence of n-BuLi. W(dNPh)((R)-(+)-5,5′,6,6′-Me 4 -3,3′-t-Bu 2 -biphenolate) 2 was found to be effective for cis-, isoselective ROMP of endo-dicyclopentadiene (DCPD), while W(dNPh)Cl 4 ‚Et 2 O promoted cis-, syndioselective ROMP. On the other hand, W(dNPh)(2,6-Me 2 -phenolate) 4 provided atactic poly(DCPD). Isotactic, atactic, and syndiotactic hydrogenated ring-opened poly(DCPD)s were characterized well by various methods for the first time. Both tactic polymers were shown to be crystalline polymers by means of DSC, WAXD, and TEM measurements. In contrast, atactic poly(DCPD) was an amorphous polymer. The crystallization rate of the syndiotactic hydrogenated poly(DCPD) was significantly higher than that of the isotactic polymer.

SYNOPSISPreparatory to triblock synthesis experiments, the cationic polymerization of a-methylstyrene (aMeSt) was investigated using the 2-chloro-2,4,4-trimethylpentane (TMPCl) / TiCl, initiating system in the presence of triethylamine (Et3N) as electron donor ( E D ) and CH3Cl/n-hexane mixed solvent in the -80 to -40°C range. Conversions are influenced by temperature, [ TiC14 J , [ Et3N J , and [ aMeSt J . The polymerization of aMeSt is living at -80°C: Both termination and chain transfer to monomer are frozen out, however, initiation is slow relative to propagation. Highly syndiotactic (>94%) PaMest was obtained. At -60°C initiator efficiency is ca. loo%, but termination becomes evident. Et3N may act both as ED and as proton scavenger. Novel poly ( a-methystyrene-b-isobutylene-b-a-methylstyrene) ( PaMeSt-PIB-PaMeSt) triblocks have been synthesized by adding aMeSt to biliving polyisobutylene carbocations (ePIBe) in the -80 to -40°C range. The effects of temperature, solvent polarity, and [ Et3N] on the block copolymerization have been investigated. At -8O"C, the rate of crossover from @PIB@ to aMeSt is lower than that of propagation of PaMeSte, so that the triblock is contaminated by PIB and PIB-b-PaMeSt. At -6O"C, crossover occurs preferentially. The rate of propagation relative to that of crossover is also reduced by lowering the solvent polarity and increasing the [ Et,N] . High crossover efficiency and blocking efficiency can be obtained under optimum blocking conditions. The triblocks are novel thermoplastic elastomers ( T P E s ) .

This article reports the synthesis and characterization of an extremely high thermostable cyclic olefin copolymer with advanced optical properties resulting from the vinyl addition copolymerization of norbornene with styrene catalyzed by a substituted fluorenylamidodimethyltitanium catalyst [Me2Si(3,6‐tBu2Flu)(tBuN)]TiMe2 activated with a [Ph3C] [B(C6F5)4]/Al(iBu)3 cocatalyst using o‐dichlorobenzene as solvent. The prepared copolymer possesses a glass transition temperature as high as polyimide (Tg > 300 °C) and a high transmittance which is comparable with that of the conventional optical resins ([T] > 90%). The incorporation of polystyrene, which exhibits a negative birefringence into the vinyl‐added polynorbornene that possesses an intrinsic positive birefringence, effectively reduced the birefringent magnitude of the norbornene‐styrene copolymer due to a mutual compensation between these opposite‐sign birefringences. The absence of any functional and aromatic heterocyclic groups and the presence of highly hydrophobic saturated bicyclic rings in the copolymer main chains effectively prevented the diffusion of water/oxygen and thus enhanced the dimensional and optical stabilities of the material. Preliminary results on the characterization of the thermal stability, mechanical, and optical properties of the vinyl‐added norbornene‐styrene copolymers indicate that they satisfy all the rigorous requirements for a polymer to be applied as a flexible substrate for the manufacturing of the flexible displays. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

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