The crystal structure of methenyltetrahydromethanopterin cyclohydrolase from Methanobrevibacter ruminantium

Methenyltetrahydromethanopterin cyclohydrolase (Mch) is involved in the methanogenesis pathway of archaea as a C₁ unit carrier where N⁵‐formyl‐tetrahydromethanopterin is converted to methenyl‐tetrahydromethanopterin. Mch from Methanobrevibacter ruminantium was cloned, purified, crystallized and its crystal structure solved at 1.37 Å resolution. A biologically active trimer, the enzyme is composed of two domains including an N‐terminal domain of six α‐helices encompassing a series of four β‐sheets and a predominantly anti‐parallel β–sheet at the C‐terminus flanked on one side by α‐helices. Sequence and structural alignments have helped identify residues involved in substrate binding and trimer formation. Proteins 2013; 81:2064–2070. © 2013 Wiley Periodicals, Inc.     

Combined effect of cyprid age and lipid content on larval attachment and metamorphosis of Balanus amphitrite darwin

Various algal diets of different lipid content and composition were used to rear batches of naupliar larvae of Balanus amphitrite. The cyprids in these larval batches differed in lipid content and were used to investigate the combined effect of cyprid lipid content and cyprid age on attachment and metamorphosis. For this purpose, cyprids were aged for 0,3 and 6 d at 8°C prior to utilization in laboratory attachment assays. The percentage attachment of cyprids with similar lipid content differed significantly among the three age categories. A strong and a weak positive relationship between cyprid lipid content and attachment were monitored in young and old cyprids, respectively. A significant interaction (two‐way ANOVA) between cyprid age and lipid content was observed, indicating that these factors jointly affect larval attachment and metamorphosis in B. amphitrite from the beginning of the cyprid stage.     

Effect of cyprid age on the settlement of balanus amphitrite darwin in response to natural biofilms

Larval settlement of the barnacle Balanus amphitrite Darwin (Cirripedia, Balanidae) is influenced by natural biofilms. In previous work by others, discriminatory settlement of aged cyprids has been observed in response to biofilms of different age. This study extends prior work by considering the effect of the age of cyprids on the outcome of settlement assays. Settlement was investigated with 0‐day‐old (newly metamorphosed) and 5‐day‐old cyprids. Biofilms under investigation were developed in the field for periods of 5 d and 1 month, and were subsequently included in laboratory settlement assays with a choice between a filmed and an unfilmed substratum. The bioassay was modified from the conventional horizontal dish design in order to generate a low water surface‐to‐volume ratio, which served to suppress larval entrapment in an organic layer on the water surface. Irrespective of cyprid age, a clear discrimination between a filmed and an unfilmed substrata was observed, and the preference for filmed or unfilmed substratum was dependent on the age of the cyprids. Settlement of 0‐day‐old cyprids was inhibited by a biofilmed substratum whereas induction occurred with aged cyprids. This pattern of settlement was independent of biofilm age. Bacterial abundance on unfilmed substrata in treatments and controls was significantly lower than that on biofilmed surfaces, confirming that bacterial contamination did not change the qualitative option during the assay.     

Civilization,wilderness and secrecy: Making two Nigerian films

This paper draws on fieldwork and filmmaking experiences and explores the interpretive process shared between the object, filmmaker, and audience. Mammy Water: In Search of the Water Spirits in Nigeria [1989] is the result of extensive field research and close collaboration between the local community, the researcher/filmmaker and team. Mammy Water priviledges local views on the subject over the academic discourse taking place elsewhere. This has evoked diverse reactions. Some miss the (Western) analytical level, others engage in the discourse itself, or assume the film's own position. The issue of cultural perspective is carried even further in cinematography. Both films discussed here were made not only in close collaboration with African communities but also photographed by an African cinematographer, Alhaji Yusufu Mohammed. His camera evokes diametrically opposed reactions from African and Western viewers. Where Westerners perceive “distance”, African audiences perceive “closeness”, where Westerners perceive a scene as “staged”, African audiences perceive it as “natural”. This contrast of perception is further highlighted in Owu: Chidi Joins the Okoroshi Secret Society [1991], mostly filmed by Alhaji, but complemented by two video inserts by my daughter, Saskia Jell, who produced additional behind‐the‐scenes footage in Coming to Nigeria.

Reviewers have raised another important topic. Owu points to three different levels of secrecy surrounding the masquerade and initiation into Oguta's Okoroshi society. This in turn raises questions on if and how to represent secrecy and the dichotomy between civilization and wilderness on film.

A discussion of post‐production at the IWF introduces a negative dimension and questions the undue impact of politics, German rigidity, and other impediments.

In conclusion, my films are strongly grounded in long‐term field research, and indebted to the people whose cultures I have researched, as well as to Alhaji Yusufu Mohammed's cinematic representation. Situated between Africa and the Western world, my films contain elements of both African and Western cultures, as they attempt to mediate between them. 1 am looking to the genre of ethnographic film primarily for its effort to create meaning in interpreting and representing cultures, for its position between the cultural worlds, and for its possibilities for transcultural communication. This goal could be served by a plurality of methods, different film styles, and varied authors within the same genre.     

Masking the mask: An Israeli response to the threat of chemical warfare

This paper analyzes a form of visual euphemism which we call “masking the mask.” During the Gulf War, Iraq fired 40 missiles on Israel. Citizens were issued with gas mask kits and were ordered into sealed rooms in their homes during attacks. Thousands of Israelis of all ages decorated or covered their gas mask kits. Although no chemical warheads were fired on the country, Israelis were unusually fearful of gassing because of associations with the Holocaust. Masking the mask served important psychological and communicative functions. It provided a means to express one's fears, to attempt a modest form of mastery over a threatening environment, as well as to rebel against dehumanization and personalization, and to express solidarity with the group under threat, while reasserting one's individual identity.     

Stereoselective Interaction Between Tetrahydropalmatine Enantiomers and CYP Enzymes in Human Liver Microsomes

Tetrahydropalmatine (THP), with one chiral center, is an alkaloid that possesses analgesic and many other pharmacological actives. The aim of the present study is to investigate stereoselective metabolism of THP enantiomers in human liver microsomes (HLM) and elucidate which cytochrome P450 (CYP) isoforms contribute to the stereoselective metabolism in HLM. Additionally, the inhibitions of THP enantiomers on activity of CYP enzymes are also investigated. The results demonstrated that (+)‐THP was preferentially metabolized by HLM. Ketoconazole (inhibitor of CYP3A4/5) inhibited metabolism of (?)‐THP or (+)‐THP at same degree, whereas the inhibition of fluvoxamine (inhibitor of CYP1A2) on metabolism of (+)‐THP was greater than that of (?)‐THP; moreover, the metabolic rate of (+)‐THP was 5.3‐fold of (?)‐THP in recombinant human CYP1A2. Meanwhile, THP enantiomers did not show obvious inhibitory effect on the activity of various CYP isoforms (CYP1A2, 2A6, 2C8, 2C9, 2C19, 2E1, and 3A4/5), whereas (?)‐THP, but not (+)‐THP, significantly inhibited the activity of CYP2D6 with the Ki value of 6.42 ± 0.38 μM. The results suggested that THP enantiomers were predominantly metabolized by CYP3A4/5 and CYP1A2 in HLM, and (+)‐THP was preferentially metabolized by CYP1A2, whereas CYP3A4/5 contributed equally to metabolism of (?)‐THP or (+)‐THP. Besides, the inhibition of CYP2D6 by (?)‐THP may cause drug–drug interaction, which should be considered. Chirality 25:43–47, 2013. © 2012 Wiley Periodicals, Inc.     

Conformational Equilibria of Bridled Chiroporphyrins in Solution Investigated by Vibrational Circular Dichroism

A series of bridled chiroporphyrins (BCP) and their metal complexes were prepared, in which two n‐methylene straps connect adjacent meso substituents by ester linkages. These compounds can exist as four atropisomers (αααα, αβαβ, αααβ, or ααββ) depending on the position of the meso groups relative to the macrocycle (α when above and β when below). We characterized the conformation of these chiral porphyrins and their metal (Zn, Ni, Mn) complexes by vibrational circular dichroism (VCD) associated with ab initio calculations. VCD spectra of the three metalloporphyrins were recorded in CDCl₃ and benzene solutions and ab initio calculations of their four atropoisomers were performed at the Density Functional Theory (DFT) level. The bridled chiroporphyrin with the longer straps (9 CH₂) and its nickel(II) complex can be isolated as the αβαβ atropisomer in the solid state and were found with the same conformation in CDCl₃ and benzene solutions. The bridled chiroporphyrin with the shortest straps (8 CH₂) and its zinc(II) complex can be isolated as the αααα atropisomer in the solid state, but in solution they are subject to atropisomeric equilibria, resulting in atropisomer distributions that are strongly solvent‐dependent. Comparison of the experimental VCD spectra with the predicted spectra of the four atropisomers allowed the quantification of these distributions. Finally, the manganese(III) complex also exhibits an atropisomeric equilibria in solution which is slightly solvent‐dependent. Chirality 25:480–486, 2013. © 2013 Wiley Periodicals, Inc.