Electrochemistry of some substituted pteridines

Some substituted 4(3H)-pteridones have been investigated by classical polarography, cyclic voltammetry, and controlled potential electrolysis; based on these results, the following reaction path for substituted 2-amino-4(3H)-pteridones seems likely. In neutral and slightly alkaline solution the first step is a reversible two-electron reduction to the unreducible 5,8-dihydro derivative, which tautomerizes into a reducible 7,8-dihydropteridone at a rate depending on the substituents. At a more negative potential the 7,8-dihydro derivative is reduced in a two-electron reaction to the unreducible 5,6,7,8-tetrahydropteridone. This compound can be oxidized in a reversible reaction to a 6,7-dihydropteridone, a “quinonoid” form, which tautomerizes into the 7,8-dihydropteridone. The data from cyclic voltammetry favour the formulation of the “quinonoid” form as the 6,7-dihydropteridone, an “o-quinonoid” structure.     

The last order of coiling in human chromosomes

The dimensions of chromatids in vivo and in fixed preparations of human chromosomes from cultured lymphocytes were compared. The relative variation in diameter in relation to length was the same in both conditions, but the lengths of the fixed chromosomes were about twice that of the chromosomes in vivo. The last order of coiling was studied in fixed chromosomes and in prematurely condensed chromosomes. The pitch of the coils in the fixed chromosomes, 0.6 μm, was independent of haploid length in the interval 90–220 μm. A clear indication of a spiralization of an underlying fibre was found throughout the haploid length interval of the prematurely condensed chromosomes, which ranged from 130 μm to more than 350 μm.     

The chaperonin cycle and protein folding

The process of protein folding in the cell is now known to depend on the action of other proteins. These proteins include molecular chaperones, Which interact non-covalently with proteins as they fold and improve the final yields of active protein in the cell. The precise mechanism by which molecular chaperones act is obscure. Experiments reported recently⁽¹⁾ show that for one molecular chaperone (Cpn60, typified by the E. coli protein GroEL), the folding reaction is driven by cycles of binding and release of the co-chaperone Cpn10 (known as GroES in E. coli). These alternate with binding and release of the unfolded protein substrate. These cycles come about because of the opposite effects of Cpn10 and unfolded protein on the Cpn60 complex: the former stabilises the ADP-bound state of Cpn60, whereas the latter stimulates ADP-ATP exchange. This model proposes that the substrate protein goes through multiple cycles of binding and release, and is released into the cavity of the Cpn60 complex where it can undergo folding without interacting with other nearby folding intermediates. This is consistent with the ability of Cpn60 proteins to enhance folding by blocking pathways to aggregation.     

Tissue-specific DNase I-sensitive sites of the maize P gene and their changes upon epimutation

A map has been developed of nuclease-hypersensitive sites of P-rr , the standard allele of the P -locus of Zea mays L. Using a traditional DNase I assay, eight such sites have been found that are specific for the expressing tissue and span a region of more than 25 kb of the P -locus, making it one of the largest plant genes yet described. The maps of the standard allele have also been compared with the recently described moderately stable P-pr allele, which arose from epimutation. Six of the eight sites exhibit the same tissue-specificity in P-pr plants, while two stay repressed as in non-expressing tissues of plants with the standard allele. Interestingly, the two repressed sites coincide with two hypermethylated restriction sites that have previously been correlated with the expression potential of the P-pr allele. On the other hand, four of the DNase I sites, coinciding with CpG islands that were not hypermethylated by the epimutation, also showed no differences in their sensitivity to DNase I between the standard allele and the P-pr allele. This suggests that the epimutation affects both site-specific methylation changes and a specific local chromatin structure of the P gene involved in its regulation.     

Roaming Companion Cats as Potential Causes of Conflict and Controversy: A Representative Questionnaire Study of the Danish Public

Cats have grown in popularity as companion animals, but there are also people who strongly dislike them. Companion cats allowed to roam freely outdoors are seen by some as a nuisance. This paper, drawing on research conducted in Denmark, aims to quantify potentially conflicting attitudes to cats among the public that may feed into cat-related conflicts and controversies. Questionnaire data were collected from a representative sample of the Danish population (n = 2,003), where 21% (n = 415) owned cats and 79% (n = 1,588) did not. In all, 65% of respondents confirmed that they liked cats, 21% reported that they did not, and 14% were undecided. The main reasons for disliking cats concerned “behavior,” not hazards such as the spread of diseases and predation. Of the 21% of the surveyed Danes who reported that they currently had a cat in the household, 72% allowed their cat to roam outdoors. Sixty percent of the respondents did not perceive this as a problem. However, the potential for conflict was demonstrated by the fact that 27% of respondents regarded outdoor roaming as problematic. Of these, about a quarter saw free-roaming cats as a big problem and as a cause of strife between neighbors. Comparatively fewer of those who owned cats saw their animals as a cause of problems. Thus, only 12% of those owning outdoor cats thought that problems were caused when their cats defecated in a neighbor’s garden, which compares with the 17% of the total population who are bothered by other people’s cats defecating in their gardens. Our data show that while the majority of Danes believe cats should be allowed to roam in public spaces, a significant minority strongly dislikes cats and would prefer restrictions on roaming.     

Expression and characterization of truncated forms of humanized L243 IgG1. Architectural features can influence synthesis of its oligosaccharide chains and affect superoxide production triggered through human Fcgamma receptor I.

The properties of IgG and its subcomponents are being exploited to generate new therapeutics with selected biological activities. In this study, a series of truncated, humanized IgG1 antibodies was expressed in Chinese hamster ovary cells, to evaluate the contribution of structural components to glycosylation and function. The series includes L243 IgG1 (alpha-MHC Class II) lacking a CH3 domain pair (DeltaCH3-IgG1), single-chain Fv fusion proteins with Fc or a hinge-CH2 domain, Fc with/out a hinge, and a single CH2 domain. Glycosylation of IgG Fc is important for recognition by effector ligands such as Fcgamma receptors. HPLC analysis of released and pyridylaminated oligosaccharides indicates that intact IgG1 and scFvFc antibodies are galactosylated and sialylated to levels similar to those observed previously for normal human IgG1. The truncated forms express increased levels of digalactosylated (30-83%) or sialylated (9-21%) oligosaccharide chains with the highest levels observed for the single CH2 domain. These data show which architectural components influence IgG glycosylation processing and that the (CH3)2 pair is particularly influential. When MHC Class II bearing (JY) cells were sensitized with L243 DeltaCH3-IgG1, scFvFc, or scFvhCH2 they elicited superoxide production, from U937 cells, at levels of 35-45% relative to that obtained for intact L243 IgG1 (100%). Mild reduction and alkylation of the hinge disulphide bonds of scFvhCH2 greatly decreased its capacity to trigger superoxide production. Thus, the L243 scFvhCH2 homo-dimer constitutes the minimal truncated form that binds the MHC Class II antigen and triggers superoxide production through FcgammaRI.