Three new Arizona types isolated from normal reptiles

Summary Three new Arizona serotypes (5∶29∶30; 16∶22∶34; and 20∶29∶25) are described. All were isolated from the feces of apparently normal snakes in a zoo. The 16∶22∶34 type produced indol and the 20∶29∶25 type failed to liquefy gelatin. Otherwise, the cultures possessed biochemical characteristics typical of the Arizona group. The details of the serologic reactions of the cultures are described.     

Crystals of modified fibrinogen: Size,shape and packing of molecules

We have produced several new macroscopic crystal forms and a variety of microcrystals from modified flbrinogens. Bovine and rabbit flbrinogens crystallize after limited digestion by a bacterial protease or α-chymotrypsin. The fibrinogens making up these crystals are largely intact and highly clottable. Tentative molecular packing arrangements for two crystal forms have been deduced. The crystal morphology and cleavage planes were used in this analysis. The characteristic α-helical coiled-coil reflections arid spikes of intensity in certain directions in the crystal X-ray patterns serve as markers for the orientation of the fibrinogen molecules. Changes that occur in one of the forms during preparation for electron microscopy, as shown by comparison with X-ray experiments on crystals in various stains and solvents, support this packing model. These studies provide preliminary evidence that fibrinogen is about 450 Å in length and that the molecules bond end-to-end to form filaments making up the crystals.