Angiotensin Converting-Enzyme （ACE） inhibitors are potential drugs for hypertension.There are three requirements to be necessary for successful inhibition of ACE:1) a functional group capable of binding to zine in the active site (i.e.carboxylate,phosphonate,or sulfhydryl);2) a carbonyl oxygen capable of accepting a hydryogen bond from some donor residue functional groups and 3) an ionizable C-terminal carboxylate moiety which interacts with positively charged residue〔1〕. We reported active conformers of some ACE inhibitor molecules,which were derived by Distance Comparison〔2〕.In this paper,the electronic structure of the lowest energy conformers and active conformers of the ACE inhibitor molecules (Figure 1) were calculated through ab initio calculation by using Gaussian94 package.The Density Functional Theory (DFT) method and 6-31G** basis set were used 〔3〕.The calculation results were listed in Table 1.The total energies、HOMO energies and the charges of the marked atoms of all active conformers were higher than that of the correspondent lowest energy conformers.They were useful clues for designing novel analogs to inhibit the activity of ACE.

Extended-spectrum β-lactamase controversies

What is an ESBL?What seemed like a simple concept when the name ESBL was introduced has become more complicated as more enzymes with related properties have been recognized. The first enzymes to be termed extended-spectrum β-lactamases (ESBLs) were found to differ from the common, plasmid-mediated, broadspectrum SHV-1, TEM-1, or TEM-2 β-lactamases by a small number of amino acid substitutions located near the active site that modified its structure so as to extend the spectrum of the parental enzyme[1-3]. Later ESBLs related to OXA-2 or OXA-10 were discovered that also differed from their progenitors by a limited number of amino acid substitutions[4-5]. These enzymes conferred resistance to oxyirnino-β-lactams such as cefotaxime, ceftazidime, ceftriaxone, and aztreonam and were at least as susceptible to β-lactamase inhibitors (clavulanic acid or sulbactam) as the parental types (with the OXA enzymes notably less susceptible than those in the TEM or SHV families)[6].