The chemistry of vitamin B12. The coordination of biologically important molecules

The following equilibrium constants (given as logK in units of m⁻¹) were determined for the substitution of co-ordinated H₂O in aquocobalamin by glycine (bound through N) 5.8, cysteine (bound through S) 6.0 or 8.3, depending on the value chosen for the pK of the thiol group, and phenolate 2.9. The spectrum of the phenolate cobalamin shows an additional intense absorption band at 468nm with a molar extinction coefficient of 1.1×10⁴, which is assigned to a charge transfer from the phenolate to the cobalt ion. Equilibrium constants have also been determined for the equilibria between adenylcobamide cyanide and CN⁻, HO⁻ and H⁺, which show that the adenine is more easily displaced by CN⁻ and HO⁻ than is 5,6-dimethylbenziminazole in vitamin B₁₂, but can be protonated by acid while still remaining co-ordinated to the cobalt. It is shown that in the binding of corrinoids to proteins and polypeptides the formation of hydrogen bonds is far more important than co-ordination by the metal.     

Survey of the U.S. Gulf Coast for the Presence of Clostridium botulinum

In sediments and animals collected during warm weather months between Key West, Fla., and Brownsville, Tex., Clostridium botulinum, predominantly type E, was demonstrable. Incidence was somewhat higher in the eastern Gulf animals, but the organism was present to the southernmost limits of both Texas and Florida. Types A and F were never detected in warm weather. No bottom type or any single species seemed exclusively vulnerable. In samples collected during colder weather, the east-west incidence differential was minimized in animals but not in sediments, overall incidence was lowered, all known types were present, and type E no longer predominated. Detection by fluorescent-antibody techniques was found to be inadequate.     

THE ORIGIN OF PROTEIN AND FATTY YOLK IN RANA PIPIENS : I. Phase Microscopy

Study of living frog oocytes with the phase microscope has shown that the early yolk appears in two forms. One of these, the protein yolk, consists of thin, dense, plate-like bodies which in face view are almost always regular hexagons. The other form, the fatty yolk, occurs as clusters of globules of varying sizes. The plate-like bodies occur both singly and in clusters. As the oocytes mature these plate-like bodies grow in size while retaining their hexagonal outline. Mitochondria have been observed to increase in length and numbers as the oocytes mature; they are rods or filaments at all stages of growth up to an oocyte diameter of 300 microns. The oocyte cytoplasm gradually becomes packed with long mitochondria, plate-like bodies, and clusters of globules.     

THE BREEDING BIOLOGY OF THE BLACK-FACED DIOCH QUELEA QUELEA IN NIGERIA

A study of the breeding biology of Quelea quelea in Nigeria, and particularly at a large breeding colony near Lake Chad, showed that losses of eggs and young were extremely small. 95% of eggs laid hatched successfully, and 87% give rise to fledglings. Nestling deaths were density-dependent and apparently due to starvation.
The incubation period was 10 days or less. By day, eggs were heated to 34°- 37° C. by the sun; at night the females incubated. The nestlings were initially fed mainly on insects, their diet gradually changing to one of seeds—mostly of the grass Echinochloa pyramidalis . The deep body temperatures of young birds were determined. It is suggested that the nestlings left the nest after, on average, 11¹/₂ days to escape intolerable temperature conditions in the nest.
Fat reserves were accumulated by nestlings and fledglings, and were utilized when the young became independent. The adults put on fat during the incubation period and lost it during the time spent feeding nestlings.
It is concluded that the most common clutch-size of Q. quelea , which is everywhere three, corresponds to the largest number of young the parents can normally nourish. This conforms to Lack's theory on the significance of clutch-size, and gives no support to Skutch's opinion that the theory does not apply to tropical birds.     

Blood-Free Medium for the Rapid Growth of Pasteurella tularensis

A medium composed of (in g/100 ml) Tryptose broth with thiamine (Difco), 2.6; cysteine-HCl, 0.12; glucose, 1; FeSO₄, 7H₂O, 0.005; KCl, 0.02; histidine, 0.1; tris(hydroxymethyl)aminomethane (tris) buffer, 0.3; and agar, 1; will support rapid growth of the fully virulent SCHU-S4 strain of Pasteurella tularensis. Although the test organism grew rapidly on medium from which KCl and tris buffer were omitted, these two components increased the stability of the medium upon storage at 4 C. It was necessary to (i) control carefully the relative concentration of the ferrous iron and cysteine-HCl, (ii) incubate the prepared medium overnight prior to use, and (iii) incubate the inoculated plates in an atmosphere of high relative humidity. Rapid growth of the organism was obtained also from very small inocula in the liquid form of the medium. Biochemical studies designed to elucidate the mechanisms involved in the enhancement of growth of P. tularensis in this relatively simple blood-free medium were initiated.