Silver-catalysed hydroamination: synthesis of functionalised pyrroles

It has been shown that functionalised pyrroles can be efficiently prepared using a two-step sequence. This sequence involves the propargylation of secondary enaminones using n-BuLi and propargyl bromide, followed by intramolecular hydroamination catalysed by silver nitrate. The hydroamination can be carried out at room temperature (overnight) or in a domestic microwave oven (60 s).     

Complete nonorientable minimal surfaces in R3

We consider complete nonorientable minimal immersionsx(M)⊇R ³. Assuming the double coverN ofM has finite total curvature, we generalize an argument of Lopez/Ros to give a sufficient condition for the instability ofx(M) in terms of the total curvature ofM and the genus γ of . We apply this condition to prove that if the immersion is regular thenx(M) is unstable. We also consider the case where the immersion is finitely branched, and we classify the possibilities under the assumption the is hyperelliptic.     

Correlation inequalities for the truncated two-point function of an Ising ferromagnet

We establish the following new correlation inequalities for the truncated twopoint function of an Ising ferromagnet in a positive external field: _j ; _l ^T _j ; _k ^T _k ; _l ^T , and _j ; _l ^T _{k K j} ; _k ^T _{k l} , whereK is any set of sites which separatesj froml. The inequalities are also valid for the pure phases with zero magnetic field at all temperatures. Above the critical temperature they reduce to known inequalities of Griffiths and Simon, respectively.NSERC Postgraduate Fellow, 1978–1981. Research supported in part by NSF Grant No. PHY-78-25390-A02.     

Recovery of intact proteins from silver stained gels

Silver stained proteins of a wide molecular weight (MW) range (20-116 kDa) were successfully recovered by both electroblot and electroelution. The recovery was demonstrated for nanogram loads of proteins separated by SDS-PAGE and visualized by silver staining methods compatible and incompatible with mass spectrometry (MS). It was shown that the alcohol/acid and glutaraldehyde fixation steps present in a number of staining procedures did not prevent recovery of intact proteins from gels. It was found that the recovery of intact proteins from silver stained gels was substantially increased upon pre-equilibration in a buffer containing the reducing agent, dithiothreitol (DTT). The effect of destaining on the recovery of silver stained proteins was also investigated. Comparable recovery of intact proteins within a wide MW range from silver stained gels with and without destaining step was demonstrated. Recovery of model proteins from gels visualized using silver staining method compatible with MS showed 52 to 76% yield of that from the unstained gel, depending upon method of the transfer. Comparison of the recovery of intact proteins from gels visualized using other staining procedures was also made. The above findings have implications as to the supposed irreversible nature of protein "fixation" inside polyacrylamide matrix, and confirm lack of binding of proteins in the gel to metal silver deposited on its surface. This method has the potential to be suitable for direct characterization of proteins by matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) without additional purification steps.     

The electrical conductivity and magnetic susceptibility of germanium(II) monoselenide in the solid and liquid states

The specific conductivity of germanium(II) monoselenide has been measured, under equilibrium pressure, from room temperature to 802°C. Interpretation of the results leads to the conclusion that the intrinsic conductivity is observed in the solid in the upper temperature range: the calculated energy gap is E_0g = 1.222 ± 0.027 eV which coincides with the value of the optical gap. In liquid GeSe the calculated energy gap is 1.504 ± 0.016 eV. This increase of the energy gap in liquid GeSe is due, presumably, to the strengthening of the intralayer bonds of the structure. Electrical conductivity and magnetic susceptibility measurements confirm the existence of a polymorphic transformation in GeSe at 656°C.