Donor substrate binding to trans-sialidase of Trypanosoma cruzi as studied by STD NMR

Using STD NMR experiments, we have studied the binding epitopes of p-nitrophenyl glycosides of sialic acid and analogs thereof when bound to Trypanosoma cruzi trans-sialidase (TSia). Time-dependent NMR spectra yielded data on the rate of substrate hydrolysis in comparison to sialic acid transfer. Our experiments clearly demonstrate that shortening of the glycerol side chain significantly favors the transfer reaction over hydrolysis. Our results extend the basis on which specific trans-sialidase inhibitors may be designed.     

Contact Doping with Sub‐Monolayers of Strong Polyelectrolytes for Organic Photovoltaics

Barriers to charge transfer at electrode‐semiconductor contacts are ubiquitous and limit the applicability of organic semiconductors in electronic devices. Molecular or ionic doping near contacts can alleviate charge injection or extraction problems by enabling charge tunneling through contact barriers, but the soft nature of organic materials allows for small molecule dopants to diffuse and migrate, degrading the performance of the device and limiting effective interfacial doping. Here, it is demonstrated that contact doping in organic electronics is possible through ionic polymer dopants, which resist diffusion or migration due to their large size. Sub‐monolayer deposition of non‐conjugated strong polyelectrolytes, e.g., sulfonated poly(sulfone)s, at the anode‐semiconductor interface of organic photovoltaics enables efficient hole extraction at the anode. The performance of contact‐doped organic photo­voltaics nearly matches the performance of devices composed of traditional hole transport layers such as poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The degree of sulfonation of the dopant polymer and the thickness of the ionic dopant layer is shown to be critical for optimizing doping and the efficiency of the device.     

Artificial N-functionalized UDP-glucosamine analogues as modified substrates for N-acetylglucosaminyl transferases

Analogues of UDP-GlcNAc modified at the 2-acetamido group of the GlcNAc moiety were prepared in order to study their role in the mechanism of N-acetylglucosaminyl transferase mediated glycosylation reactions. The structural analogues with N-formyl-, N-propionyl-, N-butyryl- and N-isobutyryl-groups were synthesized, utilizing the morpholidate coupling method starting from d-glucosaminyl-1-phosphate after selective N-acylation of its amino group with the appropriate N-acyloxysuccinimide esters as well as a chlorinated formylformiate.     

A new Trichoplusia ni cell line for membrane protein expression using a baculovirus expression vector system

A new cell line, MSU-TnT4 (TnT4), was established from Trichoplusia ni embryos for use with baculovirus expression vectors and evaluated for its potential for membrane protein production. To evaluate membrane protein synthesis, recombinant baculoviruses were constructed to express the human neurotensin receptor 1 as an enhanced green fluorescent protein (GFP) fusion. TnT4 cells had a doubling time of 21 h and expressed the membrane-GFP fusion protein at approximately twice the level as Sf21 cells from the p10 promoter, as evaluated by GFP intensity. Expression of secreted alkaline phosphatase (SEAP) was similar to that of Sf21 cells. Expression of membrane-GFP fusion proteins in recombinant baculoviruses provides a rapid method for evaluating the potential of new cell lines for the production of membrane proteins using a baculovirus expression vector system (BEVS).     

Comparative solution and solid-phase glycosylations toward a disaccharide library

A comparative study on solution-phase and solid-phase oligosaccharide synthesis was performed. A 16-member library containing all regioisomers of Glc–Glc, Glc–Gal, Gal–Glc, and Gal–Gal disaccharides was synthesized both in solution and on solid phase. The various reaction conditions for different approaches and corresponding yields are analyzed and discussed.     

Beitrag zur parthenogenese und phänologie der geschlechter von eulecanium corni bouché (coccidae)

Ohne Zusammenfassung     

Cardiac myosin subfragment 1 modification by carbodiimide in the presence of a nucleophile

The subfragment 1 from dog cardiac myosin was modified by N-cyclohexyl-N′-(2-(4-morpholinyl) ethyl) carbodiimide methyl p-toluenesulfonate in the presence of the nucleophile nitrotyrosine ethyl ester. At pH 5.9, the inactivation of ATPase activity was very rapid and followed first-order kinetics. K⁺ (EDTA) - and Ca⁺⁺-ATPase activities decreased at the same rate, and the initial phosphate burst was lost. Inactivation and incorporation of the nucleophile occurred simultaneously. Complete inactivation was accompanied by the incorporation of 1 mol of (¹⁴C) nitrotyrosine per mol of myosin subfragment 1. Inactivation and incorporation of the label were essentially equal, either with the native subfragment 1, or with the subfragment 1 in which the reactive thiols were protected by cyanylation prior to modification. No protection by nucleotides was observed. These data suggest that one carboxyl group is essential for the active conformation of cardiac myosin. This finding is in general agreement with that previously obtained with skeletal subfragment 1 (Lacombe et al. (1981) Biochemistry 20, 3648–3653) except that inactivation of cardiac subfragment 1 was not prevented by nucleotides.