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An ion pair reversed phase HPLC method for the determination of clavulanic acid has been developed. Since clavulanic acid had poor absorption O,mas 201 nm in water) in a UVregion suitable for HPLC detection, the detectability was enhanced by bathochromic shift of )maa due to solvent effect. The shifts of 2ma.., were measured with the solutions containing clavulanic acid, tetrabutylammonium bromide, and phosphate buffer salts in aqueous methanol. The magnitudes of the observed shifts were investigated with respect to pH, ionic strength, methanol content, and TBAB concentration.The results indicated that TBAB concentration was the predominant factor responsible for the bathochromic shifts. Taking account of the results together with solvent effects on the retention of clavulanic acid on hydrophobic stationary phase, HPLC condition suitable for detection and separation of clavulanic acid in urine was established as follows; mobile phase: 10 mm TBAB+0.6 mm NaH2PO4 +0.4 mat Na2HPO4 in H2O-MeOH, 10: 1 (v/v) (pH 7.02), flow rate: 1.5 ml/minute, stationary phase: LiChrosorb RP-18 (25 cm x 4.6 mm i.d.), detection: UV 220 run. The applicability of the present method is demonstrated by determining the time course of urinary excretion of clavulanic acid after oral administration of a conjugated tablet of clavulanic acid and amoxicillin to human subject. found that the conjugated dose of clavulanic acid and amoxicillin was able to clean the turbid urine of patients with amoxicillin-resistant urinary tract infections, and HEEREMA et al.11> reported a similar observation with respect to the mice with renal infections. Some information also has been published on the chemical properties of clavulanic acid; the available papers described the chemical") and kinetic" investigations of the inactivation of (3-lactamase and biosynthesis of clavulanic acid.",")The assay method so far employed in the previous works has been limited to microbiological methods. None referred to chemical and spectrometric procedures for the assays of clavulanic acid, possibly because clavulanic acid has no appreciable absorption in a UV region above 210 nm,16> and neither iodometric nor hydroxamate assays are suitable for quantitative purposes.',)The present work attempts to investigate solvent effects on shifts of clavulanic acid solutions, to find a solvent system appropriate to UV detection and separation by a reversed phase HPLC, and to demonstrate the applicability of the established method to the determination of clavulanic acid excreted in human urine.

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Summary: This paper discusses the conformational changes in a single myosin molecule directly observed using atomic force microscopy (AFM). The myosin molecules were pretreated in rigor solutions without MgATP or in relaxed solutions with various concentrations of MgATP. The images of these molecules were obtained using a tapping mode AFM. The results indicate that the orientation of the myosin's heads and tail strongly depend on the MgATP concentration. Without using MgATP, almost all of the myosin molecules are in the extended form; however, when MgATP is used, the molecules bend according to the level of MgATP concentration. The meansquare end-to-end distance of the myosin molecules is significantly shorter with p[MgATP] = 4 than with p[MgATP] = 6. The rod region did not show the same level of intensity along their length in the extended form. The rods exhibited clusters of discontinuity, which were identified as substructures. The size of these substructures change at intervals that are multiples of 14.3-14.5 nm, which reflects the periodicity of the α−helical coiled coils. The substructure clusters also correspond to the myosin crossbridge spacing in muscles (14.3 or 43 nm). These results suggest that the myosin's head bends in conjunction with the bending or tilting in the helical substructures. Conformational changes of the myosin molecule induced by MgATP seem to mimic the molecular motions in a muscle's force generation process.

Heat-induced gels were prepared from two di#erent types of frozen fish-meat (Surimi) to which rice starches had been added. All the stress-strain characteristics except yield strain of gel, prepared from second-grade Surimi, were enhanced to coincide with increases of the amount of starches added. At ,*ῌ addition, the breaking stress and strain reached the same levels as those of gel obtained from SA-grade Surimi. The addition of pregelatinized starches to SA-grade Surimi enhanced sti#ness of the gel, but decreased yield and breaking characteristics. Some characteristic values of gel added with-ῌ pre-gelatinized starches were proximal to those of gel added with +*ῌ Chinese yam.

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