EXAFS of the type-1 copper site of rusticyanin.

Extended X-ray absorption fine structure (EXAFS) spectra at the Cu K-edge have been recorded of the oxidized and reduced form at pH 3.5 of rusticyanin, the type-1 or 'blue'-copper protein from Thiobacillus ferrooxidans. The EXAFS of oxidized rusticyanin is well simulated with models assuming a ligand set of 2 N(His) and 1 S(Cys) at 1.99 and 2.16 A, respectively. Upon reduction, the average Cu-N ligand distance increases by approx. 0.08A. For both redox states studied, the fit by the simulation is significantly improved by including a contribution of an additional sulfur ligand at approx. 2.8 A. From comparison with structural data of other blue-copper proteins, it is concluded that the copper coordination environment is relatively rigid, which may be a clue to its high redox potential.

CT features of intraabdominal abscesses: prediction of successful percutaneous drainage.

Fifty-three patients with 71 intraabdominal abscesses identified on computed tomography (CT) and treated with percutaneous abscess drainage were evaluated for the possible predictive value of any particular CT feature in relation to the outcome of percutaneous drainage. Features analyzed included the presence of a "rind," sharp exterior margin, air-fluid level, scattered internal gas bubbles, and internal septations, as well as size, site, and the presence or absence of fistulas as determined by sinography. Statistical analysis revealed that only site has predictive value; liver and subphrenic abscesses were more likely to have a successful outcome than abscesses in other locations (84% vs 47% complete cure). The presence of a long air-fluid level denoted communication with the gastrointestinal tract, which led to significantly longer drainage times and larger drainage volumes. Since there are no CT features that can strongly predict a poor outcome, all intraabdominal abscesses should be considered candidates for percutaneous drainage.

An extended-X-ray-absorption-fine-structure (e.x.a.f.s.) study of coenzyme F430 from Methanobacterium thermoautotrophicum.

Coenzyme F430 is a nickel porphinoid found in all methanogenic bacteria. Extended-X-ray-absorption-fine-structure (e.x.a.f.s.) spectra have been recorded above the nickel K-edge of coenzyme F430 and two model compounds, (5,10,15,20-tetramethylporphinato) nickel(II) and (5,10,15,20-tetramethylchlorinato)-nickel(II). The results show that the four nickel-nitrogen distances in F430 are split, with two nitrogen atoms at 0.192 nm and two at 0.210 nm.

The nickel ion environment in jack bean urease.

Preliminary results of an extended X-ray absorption fine structure (e.x.a.f.s.) and X-ray absorption near edge structure study of jack bean urease have recently been reported [Hasnain & Piggott (1983) Biochem. Biophys. Res. Commun. 112, 279]. These results indicate that the environment of the nickel ion in the enzyme is similar to that in the model compounds Ni(L)2(L')1(ClO4)1 (where L is 1-n-propyl-2-alpha-hydroxybenzylbenzimidazole and L' is the deprotonated form) and Ni(HMB)3(Br)2 (where HMB is 2-hydroxymethylbenzimidazole), the closest similarity being with Ni(L)2-(L')1(ClO4)1. A detailed e.x.a.f.s. analysis has now been carried out and the crystal structures of the two model compounds solved. These results are reported here.

An EXAFS study of jack bean urease, a nickel metalloenzyme.

EXAFS and XANES spectra have been recorded above the nickel K edge of urease and three model compounds. Preliminary results indicate that the local environment of the nickel ions in urease resemble most closely that of the nickel ions in the model compound [Ni(L)2(L*)1] (ClO4)1, where L is 1-n-propyl-2-alpha-hydroxybenzyl benzimidazole and L* is the deprotonated form.

Learning by experience. A student residential workshop in hospital.

A four-day residential workshop was conducted for students beginning their clinical studies at the St George Hospital in 1974. The aim of the workshop was that the students should understand the functioning of the hospital and feel comfortable as students in the hospital, so that they would learn their clinical skills more effectively in their subsequent years at the hospital. Each student lived in a hospital bed with an "illness" for two days, and spent another two days helping care for these "student patients" and exploring the hospital. Evaluation at the end of the workshop suggested that the objectives had been achieved.