Bidirectional binding of the TATA box binding protein to the TATA box

By selective attachment of a DNA cleavage agent to specific residues in the yeast TATA box binding protein (yTBP), we demonstrate that, in solution, yTBP binds to the TATA boxes of both the adenovirus major late promoter and the yeast CYC1 promoter with only a modest preference in orientation and binds well to several overlapping binding sites. The general factors TFIIA and TFIIB each increase the rotational and translational selectivity of yTBP but are not sufficient, at least individually, to confer a unique polarity to the preinitiation complex. We conclude that TBP alone cannot define the productive orientation of general factor assembly on a promoter.

Preparation of platelet concentrates after overnight hold at 20 degrees C

The clinical demand for platelet concentrates has increased dramatically in the last decade, and poses logistical problems for regional transfusion centres. Pietersz et al. (Vox Sang 1989; 56: 145-150) have shown that it is possible to prepare clinically effective platelet concentrates with substantially reduced white cell contamination, whilst maintaining satisfactory levels of factor VIII:C after holding whole blood at 20 degrees C overnight. This approach offers a method of production that will allow platelet concentrates to be prepared from potentially all donations collected, without resorting to extensive out-of-hours working. Following laboratory evaluation of the procedure we were able to reproduce Pietersz's findings, although hypotonic shock response results were less favourable than observed in our routine platelet concentrates.

Naphthyl- and quinolylluciferin: green and red light emitting firefly luciferin analogues

In the course of investigations on the possible involvement of the CIEEL (chemically initiated electron-exchange luminescence) mechanism in firefly bioluminescence, we have synthesized two novel firefly luciferin substrate analogues. D-Naphthylluciferin and D-quinolylluciferin were prepared by condensing D-cysteine with 2-cyano-6-hydroxynaphthalene and 2-cyano-6-hydroxyquinoline, respectively. These analogues are the first examples of bioluminescent substrates for firefly luciferase that do not contain a benzothiazole moiety. Firefly luciferase-catalyzed bioluminescence emission spectra revealed that compared to the normal yellow-green light of luciferin (lambda max = 559 nm), the emission from naphthylluciferin is significantly blue-shifted (lambda max = 524 nm); whereas quinolylluciferin emits orange-red light (lambda max = 608 nm). The fluorescence emission spectra, reaction pH optima, relative light yields, light emission kinetics and KM values of the analogues also were measured and compared to those of luciferin. Neither of the analogues produced the characteristic flash kinetics observed for the natural substrate. Instead, slower rise times to peak emission intensity were recorded. It appears that the formation of an intermediate from the analogue adenylates prior to the addition of oxygen is responsible for the slow rise times. The synthetic substrate analogues described here should be useful for future mechanistic studies.

What is the 'optimum' optimal additive solution?

Spontaneous formation of clotted material occurs occasionally in all stored red cell units, but larger amounts have been noted in SAG-M optimal additive suspensions. These can be substantially reduced by substitution of the SAG-M solution by a SAG-M/CPDA-1 mixture suggesting that there is insufficient citrate in SAG-M red cell suspensions to completely inhibit coagulation of the residual plasma.