OP0595 acts in three ways: (i) as an inhibitor of class A and C β-lactamases, covalently binding at their active sites; (ii) as an antibacterial, by inhibiting PBP2 of several Enterobacteriaceae; and (iii) as an 'enhancer' of β-lactam agents that bind to other PBPs besides PBP2 for several Enterobacteriaceae. OP0595 has considerable potential to overcome resistance when it is combined with various β-lactam agents.

A new beta-lactamase inhibitor, a methylidene penem having a 5,6-dihydro-8H-imidazo[2,1-c][1,4]oxazine heterocyclic substituent at the C6 position with a Z configuration, irreversibly inhibits both class A and class C serine beta-lactamases with IC(50) values of 0.4 and 9.0 nM for TEM-1 and SHV-1 (class A), respectively, and 4.8 nM in AmpC (class C) beta-lactamases. The compound also inhibits irreversibly the class C extended-spectrum GC1 beta-lactamase (IC(50) = 6.2 nM). High-resolution crystallographic structures of a reaction intermediate of (5R)-(6Z)-6-(5,6-dihydro-8H-imidazo[2,1-c][1,4]oxazin-2-ylmethylene)-7-oxo-4-thia-1-azabicyclo[3.2.0]hept-2-ene-3-carboxylic acid 1 with the SHV-1 beta-lactamase and with the GC1 beta-lactamase have been determined by X-ray diffraction to resolutions of 1.10 and 1.38 A, respectively. The two complexes were refined to crystallographic R-factors (R(free)) of 0.141 (0.186) and 0.138 (0.202), respectively. Cryoquenching of the reaction of 1 with each beta-lactamase crystal produced a common, covalently bound intermediate. After acylation of the serine, a nucleophilic attack by the departing thiolate on the C6' atom yielded a novel seven-membered 1,4-thiazepine ring having R stereochemistry at the new C7 moiety. The orientation of this ring in each complex differs by a 180 degrees rotation about the bond to the acylated serine. The acyl ester bond is stabilized to hydrolysis through resonance stabilization with the dihydrothiazepine ring and by low occupancy or disorder of hydrolytic water molecules. In the class A complex, the buried water molecule on the alpha-face of the ester bond appears to be loosely bound or absent. In the class C complex, a water molecule on the beta-face is disordered and poorly activated for hydrolysis. Here, the acyl intermediate is unable to assist its own hydrolysis, as is thought to occur with many class C substrates.

The characteristics of dislocation behavior and mechanical strength in tensile tests are investigated on the silicon crystals that are doped with nitrogen at the time of crystal growth by the floating-zone technique. These are compared with those in the usual floating-zone-grown silicon crystals. Nitrogen atoms dispersed in a silicon crystal are shown to have no influence on the velocities of dislocations in motion in the temperature range above 600 °C. Dislocations in the nitrogen-doped crystal are, however, immobilized while the crystal is kept under a low or zero applied stress at elevated temperatures. Like Czochralski-grown silicon, nitrogen-doped silicon shows a much higher yield strength than usual floating-zone-grown silicon when crystals are dislocated. It is concluded that interstitial nitrogen atoms bring about the hardening of silicon crystals through locking of dislocations upon congregating on the latter.

Outdiffusion profiles of nitrogen in silicon were measured by secondary ion mass spectrometry to determine its diffusion coefficient in a temperature range of 800–1200 °C. The total amount of the nitrogen outdiffusion agrees with the change in infrared absorption by heat treatment. The experimental results give the diffusion coefficient of nitrogen as D=2.7×103 exp(−2.8eV/kT)cm2/s. This value is five orders of magnitude larger compared with the reported expression of 0.87 exp(−3.29eV/kT)cm2/s. Nitrogen–nitrogen-pair-like molecule in crystals corresponds to the former value and substitutional nitrogen atom to the latter one. These two types of nitrogen in silicon may allow us to clarify the various effects of nitrogen such as strengthening of crystals and suppression of swirls and D-defect generation.

The design and synthesis of a series of seven tricyclic 6-methylidene penems as novel class A and C serine beta-lactamase inhibitors is described. These compounds proved to be very potent inhibitors of the TEM-1 and AmpC beta-lactamases and less so against the class B metallo-beta-lactamase CcrA. In combination with piperacillin, their in vitro activities enhanced susceptibility of all class C resistant strains from various bacteria. Crystallographic structures of a serine-bound reaction intermediate of 17 with the class A SHV-1 and class C GC1 enzymes have been established to resolutions of 2.0 and 1.4 A, respectively, and refined to R-factors equal 0.163 and 0.145. In both beta-lactamases, a seven-membered 1,4-thiazepine ring has formed. The stereogenic C7 atom in the ring has the R configuration in the SHV-1 intermediate and has both R and S configurations in the GC1 intermediate. Hydrophobic stacking interactions between the tricyclic C7 substituent and a tyrosine side chain, rather than electrostatic or hydrogen bonding by the C3 carboxylic acid group, dominate in both complexes. The formation of the 1,4- thiazepine ring structures is proposed based on a 7-endo-trig cyclization.

Optical absorption of silicon crystals involving nitrogen and oxygen is investigated at low temperature. New absorption lines are found and attributed to seven defect levels that act as shallow donors. The characteristics of the absorption lines are well described by the effective mass approximation. Five among these seven levels are related to complexes of nitrogen and oxygen atoms.

It is demonstrated that the multiple internal reflection infrared (IR) spectroscopy using a germanium prism is a very powerful nondestructive diagnostic technique for the study of silicon wafer surfaces in a wide range of IR irradiation region. The technique limits neither the shape of samples nor the IR range due to the absorption by silicon itself. With this technique, it is demonstrated that; (i) dangling bonds of a silicon surface treated with HF solution and de-ionized (DI) water are terminated mostly with H atoms, (ii) native oxide growth is enhanced by DI water rinsing, and the interstitial oxygen concentration in the silicon surface region increases during native oxide growth process, and (iii) DI water rinsing after HF etching replaces Si—F bonds with Si—H and Si—OH bonds on a silicon surface.

Novel penem molecules with heterocycle substitutions at the 6 position via a methylidene linkage were investigated for their activities and efficacy as ␤-lactamase inhibitors. The concentrations of these molecules that resulted in 50% inhibition of enzyme activity were 0.4 to 3.1 nM for the TEM-1 enzyme, 7.8 to 72 nM for Imi-1, 1.5 to 4.8 nM for AmpC, and 14 to 260 nM for a CcrA metalloenzyme. All the inhibitors were more stable than imipenem against hydrolysis by hog and human dehydropeptidases. Piperacillin was combined with a constant 4-g/ml concentration of each inhibitor for MIC determinations. The combinations reduced piperacillin MICs by 2-to 32-fold for extended-spectrum ␤-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae strains. The MICs for piperacillin-resistant (MIC of piperacillin, >64 g/ml) strains of Enterobacter spp., Citrobacter spp., and Serratia spp. were reduced to the level of susceptibility (MIC of piperacillin, <16 g/ml) when the drug was combined with 4, 2, or 1 g of these penem inhibitors/ml. Protection against acute lethal bacterial infections with class A and C ␤-lactamase-and ESBL-producing organisms in mice was also demonstrated with piperacillin plus inhibitor. Median effective doses were reduced by approximately two-to eightfold compared to those of piperacillin alone when the drug was combined with the various inhibitors at a 4:1 ratio. Pharmacokinetic analysis after intravenous administration of the various inhibitors showed mean residence times of 0.1 to 0.5 h, clearance rates of 15 to 81 ml/min/kg, and volumes of distribution between 0.4 and 2.5 liters/kg. The novel methylidene penem molecules inhibit both class A and class C enzymes and warrant further investigation for potential as therapeutic agents when used in combination with a ␤-lactam antibiotic.