Transport of iron by mycobactin in

The uptake of ⁵⁵FeCl₃ and ⁵⁵Fe-mycobactin has been followed. FeCl₃ was the more effective source of iron for the cell although Fe-mycobactin was adsorbed on to the cell very quickly. The mycobactin within the cell is the prime receptor for Fe³⁺ and it probably functions as an ionophore for the transport of iron across the lipid envelope of the cell. Release of iron from mycobactin occurs by a NADH-dependent reductase forming Fe²⁺ and conditions for observing the activity of this unique enzyme are given.     

Interaction of guanosine 5′-diphosphate, 2′-(or 3′-) diphosphate(ppGpp) with elongation factors from

The interactions of guanosine 5′-diphosphate, 2′-(or 3′-) diphosphate(ppGpp) with the polypeptide elongation factors Tu(EF Tu) and G(EF G) have been studied. The data indicate that ppGpp binds with EF Tu to form an EF Tu-ppGpp complex, and inhibits, in a competitive manner, the exchange reaction of Tu-GDP and ³H-GDP. The ribosome-dependent GTPase reaction catalyzed by EF G is also depressed by ppGpp.     

Phase-polarisation contrast for surface plasmon resonance biosensors

A technique of phase-polarisation contrast (PPC) for the enhancement of the contrast of a surface plasmon resonance (SPR) intensity profile is proposed and experimentally realised. The technique exploits the peculiarities of light phase and polarisation behaviour under SPR. It applies to non-optimum SPR coupling conditions and enables one to lower the resonant minimum of reflected intensity nearly to zero, and hence to increase substantially the ratio of the intensity from the resonance to that at the minimum. We observed the contrast enhancement by more than one order of magnitude when we applied the PPC scheme. The PPC can be efficiently employed in commercial SPR sensors, as it significantly reduces restrictions on allowable parameters of SPR-supporting metal films and biomolecular layers immobilised on them, facilitates SPR observation, and increases the accuracy of SPR shift measurements.