Alteration of the Route to Menaquinone towards Isochorismate-Derived Metabolites

Chorismate and isochorismate constitute branch-point intermediates in the biosynthesis of many aromatic metabolites in microorganisms and plants. To obtain unnatural compounds, we modified the route to menaquinone in Escherichia coli. We propose a model for the binding of isochorismate to the active site of MenD ((1R,2S, 5S,6S)-2-succinyl-5-enolpyruvyl-6-hydroxycyclohex-3-ene-1-carboxylate (SEPHCHC) synthase) that explains the outcome of the native reaction with α-ketoglutarate. We have rationally designed variants of MenD for the conversion of several isochorismate analogues. The double-variant Asn117Arg–Leu478Thr preferentially converts (5S,6S)-5,6-dihydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHD), the hydrolysis product of isochorismate, with a >70-fold higher ratio than that for the wild type. The single-variant Arg107Ile uses (5S,6S)-6-amino-5-hydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHA) as substrate with >6-fold conversion compared to wild-type MenD. The novel compounds have been made accessible in vivo (up to 5.3 g L⁻¹). Unexpectedly, as the identified residues such as Arg107 are highly conserved (>94 %), some of the designed variations can be found in wild-type SEPHCHC synthases from other bacteria (Arg107Lys, 0.3 %). This raises the question for the possible natural occurrence of as yet unexplored branches of the shikimate pathway.     

Inhalation toxicity of 1,6-hexanediamine dihydrochloride in F344/N rats and B6C3F1 mice

1,6-Hexanediamine (HDA) is a high production volume chemical which is used as an intermediate in the synthesis of paints, resins, inks, and textiles and as a corrosion inhibitor in lubricants. Two- and 13-week studies of the toxicity of the dihydrochloride salt of HDA (HDDC) were conducted in male and female Fischer 344/N rats and B6C3F1 mice using whole-body inhalation exposure. Both species were evaluated for histopathologic and reproductive effects, and rats were examined for clinical chemistry and hematologic changes. In the 2-week inhalation studies, animals were exposed to 10-800 mg HDDC/m3, 6 hr per day. All rats, all female mice, and two of five male mice in the high-exposure group died before the end of the study. Surviving mice in this group had a dose-dependent depression in body weight gain. Clinical signs were primarily related to upper respiratory tract irritation and included dyspnea and nasal discharge in both species. Treatment-related histopathologic lesions included inflammation and necrosis of the laryngeal epithelium of both species and the tracheal epithelium of mice, as well as focal inflammation and ulceration of the respiratory and olfactory nasal mucosa. In the 13-week inhalation studies, animals were exposed to HDDC at concentrations of 1.6-160 mg/m3 for 6 hr per day, 5 days per week. In addition to the base study groups, a supplemental group of rats at each exposure level was included to assess the effect of HDDC on reproduction. No treatment-related changes in organ weights or organ-to-body-weight ratios occurred in rats, and no treatment-related clinical signs or gross lesions were seen in either species. Chemical-related microscopic lesions were limited to the upper respiratory tract (larynx and nasal passages) in the two highest exposure groups and were similar in both species. These lesions included minimal to mild focal erosion, ulceration, inflammation, and hyperplasia of the laryngeal epithelium, in addition to degeneration of the olfactory and respiratory nasal epithelium. HDDC caused no significant changes in sperm morphology or vaginal cytology and no significant adverse effects on reproduction in rats or mice. Hematologic and clinical chemistry changes in rats were minor and sporadic and were not accompanied by related histologic findings. HDDC did not increase the frequency of micronucleated erythrocytes in mice.(ABSTRACT TRUNCATED AT 400 WORDS)     

Synthesis of Aminopyridazines from Aminocyclopropenylium Salts and Diazomethyl Compounds [1]

Amino-substituted cyclopropenylium salts ( 11a,b ) react with diazomethyl compounds ( 12a-i ) in dichloromethane or acetonitrile in the presence of a base (ethyldiisopropylamine, 1,5-diazabicyclo[4.3.0] non-5-ene) to form 4-aminopyridazines ( 13a-i ) specifically. The reaction is interpreted in terms of an initial electrophilic diazoalkane substitution to give diazomethylcyclopropenes ( 11 + 12 → 14 ) which undergo a [1.5]-cyclisation to form the betaines 16 which, in turn, isomerise with opening of the bridging bond to give the aminopyridazines 13 . In a similar manner, the tris[amino] cyclopropenylium salts 8a,b and 10a-c are converted to the 3,4,5-tris[amino]-pyridazines ( 21a-k ) by treatment with diazomethyl compounds ( 12a, c-f ).     

Isolation and Spectroscopic Characterization of Eu@C72

A new Eu-endohedral fullerene cage, namely, Eu@C₇₂, was synthesized, separated, and a single isomer, Eu@C₇₂-I, has been isolated by multi-step HPLC for the first time and characterized by LDI-TOF mass spectrometry, UV-Vis and EPR spectroscopy. Additionally, a second isomer, Eu@C₇₂-II, has been separated by HPLC and identified by LDI-TOF mass spectrometry.     

A Profile of Psychologists' Views of Critical Risk Factors for Completed Suicide in Older Adults.

The ability to accurately and reliably predict whether an older adult will commit suicide has eluded clinicians and researchers. A random national sample of psychologists who work with older adults was surveyed regarding their perception of 36 risk factors for completed suicide and indirect self-destructive behavior in older adults. This study produced a profile of psychologists' assessment and treatment practices when working with suicidal older adults. Determining what psychologists consider to be the most salient risk factors for completed suicide is important in identifying a minimum standard that clinicians should follow when assessing older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Introduction to the special series: HIV infection among drug abusers.

Drug users are particularly at risk for contracting the human immunodeficiency virus and serve as a major mechanism for spreading the virus to other sectors of the population. As a result drug abuse treatment and potential behavioral change strategies are primary public health issues. The purpose of this article is to review the contributions included in this special edition, which represent an effort to describe the most current thinking in the field with a blend of theoretical, review, and empirical articles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Telephone booster sessions for optimizing smoking cessation for patients in rehabilitation centers.

Smokers with smoking-related diseases who are hospitalized in rehabilitation centers should be offered smoking cessation. This is the first study evaluating whether telephone booster sessions after intensive inpatient treatment are an effective strategy. The present study was conducted in 13 rehabilitation centers for somatic disorders as a prospective multicenter study with a randomized treatment-control group design. We compared abstinence rates after hospital discharge from treatment that included a group smoking cessation program with (treatment group) and without telephone booster sessions (control group). Data from 290 smokers were analyzed. After 6 and 12 months the treatment group achieved abstinence rates twice as high as those of the control group. Men profited more from telephone booster sessions than did women. Results indicated that telephone booster sessions were highly effective (even) after an inherently intensive group program during a hospital stay. Further research should focus on the special needs of women receiving telephone counseling.     

A detailed analysis of ambipolar diffusion in nanostructured metal oxide films

In this paper a transport equation is derived which describes the behaviour of the nanostructured metal oxide films in a photoelectrochemical cell. It is shown that a detailed analysis of the charge compensation mechanism necessarily leads to a transport equation with characteristics similar to but logically distinct from the pure diffusion equation. The studied phenomenon was named ambipolar diffusion in the early 1950s. It takes into account the fact that the diffusion processes of ions and electrons occur at different speeds. A weak electric field therefore couples the processes together to preserve charge neutrality. The electric field in turn affects the transport resulting in a deviation from purely diffusive behaviour. However, this has not been widely recognised in the literature for nanostructured semiconductor films until very recently. In this paper a detailed analysis is presented. It is based on the assumption that the current density is solenoidal. It is shown that application of the ambipolar diffusion model to a photoelectrochemical cell based on a nanostructured metal oxide film leads to an additional term in the transport equation, rather than only a new diffusion coefficient as in earlier work. It is also shown that the boundary conditions interact closely with the equation to form a transport model.