The subunit composition of Portunus trituberculatus hemocyanin polymers

The subunit composition of isolated polymeric forms of Portunus trituberculatus hemocyanin were analysed by immunological techniques. The dodecamers contain four monomeric subunits corresponding to subunits I, II, III and IV, whereas the hexamers are devoid of subunit IV. These results suggest that subunit IV is required as a joining piece for the assembly of dodecamers.     

Additives and Enzyme Stability

The polypeptide chain of an enzyme is folded so that the necessary functional groups are brought together in the active site. Conformational changes may disrupt this arrangement and cause loss of enzymic activity. The effect of soluble additives on the unfolding process is discussed. Additives may be classified as substrates and similar ligands, small uncharged organic molecules, specific and non-specific ionic species, and polymers.     

Extracellular secretion of levansucrase from Zymomonas mobilis in Escherichia coli

Secretion of levansucrase from Zymomonas mobilis in Escherichiacoli by glycine supplement was investigated. A significant amount of levansucrase (about 25% of total activity) was found in intact whole-cells. Cell fractionation experiments showed that levansucrase was found both in the periplasmic space and in the cytoplasmic fraction of E. coli. None or only trace amounts of levansucrase was detected in the extracellular culture broth at 24 h of cultivation and it accrued with the increasing concentration of glycine in the culture medium and duration of the culture period. Optimal glycine concentration for the maximum secretion of levansucrase was in the range of 0.8-1%, in which approximately 20-50% of levansucrase was released into the extracellular fraction at 24 h of cultivation, although glycine retarded the bacterial growth.     

Use of restriction endonucleases and exonuclease III to expose halogenated pyrimidines for immunochemical staining

We describe an enzymatic procedure for exposure of single-stranded DNA (ssDNA) containing the halogenated pyrimidines (HdUrd) bromodeoxyuridine (BrdUrd) or iododeoxyuridine (IdUrd) in single cells to antibodies that bind to HrdUrd only in ssDNA. Production of ssDNA was accomplished by digesting the DNA using either restriction endonucleases alone or endonucleases followed by exonuclease III. The enzymatic production of ssDNA was maximal when 0.1 N HCl or 0.1 M citric acid plus Triton X-100 was added to extract nuclear proteins prior to enzymatic denaturation. The restriction endonucleases Bam HI, Dde I, Eco RI, and Hind III produced significant ssDNA when used alone to allow binding of detectable amounts of the anti-HdUrd antibody IU-4 in Chinese hamster ovary cells labeled with 10 microM BrdUrd or 10 microM IdUrd. However, these treatments did not expose sufficient ssDNA to allow binding of IU-1, an anti-HdUrd antibody with lower binding affinity. IU-4 binding was most intense after treatment with Eco RI. Treatment with exonuclease III following endonuclease digestion allowed substantially more IU-4 binding.     

Concerning the structure of photobilirubin II.

Evidence is presented which supports the postulate that the photobilirubins IIA and IIB are diastereoisomers in which the C-3 vinyl group has cyclized intramolecularly. The evidence comes principally from proton n.m.r. spectroscopy at 400 MHz and from chemical considerations. The cyclic structures require the E-configuration at the C-4 double bond in the precursor; this is the first structural evidence for the Z leads to E isomerization in bilirubin and supports the view that the precursor (photobilirubin IA or IB) is (4E, 15Z)-bilirubin. Brief irradiation of photobilirubin II gives bilirubin, a new compound (photobilirubin III) and unchanged starting material. The various photoisomers are discussed in terms of their inter-relationships and biological fates.     

Plasma arginine vasotocin and angiotensin II in the water deprived Kelp gull (Larus dominicanus), Cape gannet (Sula capensis) and Jackass penguin (Spheniscus demersus)

1. The basal levels of the osmoregulatory hormones, arginine vasotocin (AVT) and angiotensin II (AII) were measured (by radioimmunoassay) in the plasma of conscious Kelp gulls, Cape gannets and Jackass penguins. 2. The responses of the hormones to similar degrees of hypertonicity and hypovolemia caused by water deprivation have also been determined. 3. Dehydration elevated plasma AVT and plasma AII in all three species. 4. The AVT concentration was increased by 2-4 fold and although in each case the correlation between plasma osmolality and plasma AVT was highly significant (2P less than 0.01), the sensitivity of release was greater in the gull (1.13 pg/ml per mOsm/kg) than in the gannet (0.36 pg/ml per mOsm/kg) or penguin (0.44 pg/ml per mOsm/kg). 5. Dehydration increased plasma AII 3-fold in the three bird types.