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In the process of developing a method for the synthesis of membrane proteins, the conditions for native chemical ligation, namely, detergent concentration and the chemical characteristics of the thiol additive were investigated in detail. The C-terminal region of the opioid receptor like 1, ORL1(288-370), which contains C-terminal intracellular and transmembrane domains, was chosen as a model. The building blocks, ORL1(329-370) and ORL1(288-328)-SR-Gly-Arg(5)-Leu (-SR- : -SCH(2)CH(2)CO-) were most effectively condensed slightly below the critical micelle concentration of SDS and in the presence of mercaptoethanesulfonic acid as a thiol additive. The results showed that the concentration of SDS and the charge on the thiol additive are crucial factors for the effective synthesis of a membrane protein by native chemical ligation.

In challenging a direct observation of the vacancy in crystalline silicon, we have carried out lowtemperature ultrasonic measurements down to 20 mK. The longitudinal elastic constants of non-doped and B-doped crystalline silicons, which were grown by a floating zone (FZ) method in commercial base, reveal the elastic softening proportional to the reciprocal temperature below 20 K. The applied magnetic fields turn the elastic softening of the B-doped FZ silicon to a temperature-independent behavior, while the fields up to 16 T do not affect the elastic softening of the non-doped FZ silicon. We present a plausible scenario for this result. Namely the vacancy with the non-magnetic charge state V 0 in the nondoped silicon and the magnetic V þ in the B-doped silicon is responsible for the low-temperature softening of the shear elastic constants ðC 11 À C 12 Þ=2 and C 44 , which can be described in terms of the quadrupole susceptibility due to the Jahn-Teller effect.

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