Determination of Docosahexaenoic Acid and n-3 Fatty Acids in Refined Fish Oils by H-NMR Spectroscopy: IUPAC Interlaboratory Study

A high-resolution proton nuclear magnetic resonance (NMR) method for determining the concentration (mg/g) of docosahexaenoic acid (DHA), the molar proportion (mol%) of DHA, and the molar proportion of total n-3 fatty acids in fish oils was validated by an IUPAC interlaboratory study (the Commission VI-6 on Oils, Fats, and Derivatives WG 3/98). Thirteen laboratories from 5 countries tested 6 pairs of blind duplicate fish oils: a refined tuna oil, 2 extracted tuna oils, an extracted bonito oil, an extracted salmon oil, and an extracted sardine oil ranging from 9 to 30 mol% DHA and from 20 to 35 mol% n-3 fatty acids. Before 1D-proton NMR measurements with 300–500 MHz instruments, oil samples were weighed and diluted with deuterochloroform solution containing ethylene glycol dimethyl ether as internal standard. To achieve precise performance, a detailed procedure for signal area measurement was described in the protocol, and all participants were instructed about the critical importance of following the protocol. Statistical performances with invalid and outlier data removed were as follows: repeatability relative standard deviations (RSDr) ranged from 0.91 to 2.62% and reproducibility relative standard deviation (RSDR) ranged from 1.73 to 4.27% for DHA concentration (mg/g); RSDr ranged from 0.39 to 2.06%, and RSDR ranged from 0.59 to 3.46% for mol% DHA; RSDr ranged from 0.23 to 0.90% and RSDR ranged from 0.85 to 2.01% for mol% total n-3 fatty acids. The method is expected to be recommended by IUPAC.

Awareness about the persons with disability act among leprosy patients and other disabled persons

To assess the level of awareness about the different provisions of the Persons with Disability Act (PWD Act) among leprosy patients and other disabled, 233 disabled persons from the self-help groups formed by Vadathorasalur Leprosy Control Unit have been interviewed using a structured interview checklist. The results show that 74.7% of the respondents were aware that identity cards are available for the disabled, 56.2% were aware of the free education benefit to the disabled, as low as 35.6% were aware of the scholarships, 33% knew about the employment reservations, 24.9% heard about the housing scheme of the government for the disabled, but 24.5% only knew about law against discrimination, 31.8% came in contact with institutions for the severely disabled and only 16% were aware of the unemployment allowance to the disabled. The level of awareness is low among women with regard to all components of the Act. It was found that students studying up to secondary level were not aware of the availability of scholarships and free education, which needs to be seriously looked into, especially by educational institutions. The level of formal education played a significant role in increasing awareness about the Act among literates. The knowledge is low among persons of all occupations. The study showed that there is a great need for an educational intervention programme to publicize the provisions of the Act among the disabled and their families.

Validity of the time trade-off and standard gamble methods of utility assessment in retinal patients

AIM

To assess the validity of the time trade-off (TTO) and standard reference gamble (SRG) techniques of utility assessment in patients with retinal disease. A cross section of eligible patients was studied and validity was determined through their relation with two logical constructs, visual acuity and scores from the Visual Function 14 (VF-14) index.

METHODS

The study consisted of eligible patients presenting to a tertiary retinal facility who completed an interview. All patients had best corrected vision of 20/40 or worse in at least one eye. TTO and SRG utilities, as well as a VF-14 questionnaire, were administered through a standardised interview. Demographic and clinical (including Snellen visual acuity) information was also collected.

RESULTS

323 patients met these study criteria. Significant predictors of TTO utilities in the multivariate analysis were vision in the better seeing eye (p<0.01) and VF-14 scores (p<0.01). Significant predictors of standard gamble utilities were also vision in the better seeing eye (p<0.01) and VF-14 scores (p<0.05).

CONCLUSION

Both the standard gamble and TTO methods demonstrate strong validity when evaluated against visual acuity in the better seeing eye and the VF-14 score.

Natural deuterium distribution in long-chain fatty acids is nonstatistical: a site-specific study by quantitative (2)H NMR spectroscopy

Quantitative (2)H NMR spectroscopy has been used to study the site-specific natural occurrence of (2)H in common unsaturated fatty acids. A marked nonstatistical isotopic distribution of (2)H is observed in both methyl oleate and methyl linoleate. By chemical modification, the internal isotopic (2)H signatures of these products have been partially accessed. Notably, it can be seen that (1) the sites of desaturation show a strong impoverishment at only one ethylenic position of each desaturation; (2) the level of impoverishment reflects the source of the hydrogen atoms present; and (3) a gradient of (2)H content occurs along the chain. These effects can in part be related to the mechanisms proposed for the enzymes responsible for the various steps of biosynthesis of unsaturated fatty acids in plants.

Determination of substrate and product concentrations in lactic acid bacterial fermentations by proton NMR using the ERETIC method

A 1H NMR method is described for the determination of the concentration of a chemically diverse group of metabolites over a wide concentration range in fermentation medium. The method employs the use of the ERETIC signal, which produces a pseudo-FID acquired with the FID derived from the sample components. It is shown that this signal, once calibrated against an external standard solution, can be used to determine accurately the concentration of all components present in the medium. The method is rapid, reliable, and applicable to a wide range of biological fluids. Problems such as the invisibility of certain components in the spectrum are overcome by a simple regulation of the pH.

The conformation of an inhibitor bound to the gastric proton pump

Substituted imidazo[1,2-a]pyridines are pharmaceutically important small molecule inhibitors of the gastric H+/K+-ATPase, the membrane-bound therapeutic target for peptic ulcer disease. A non-perturbing analytical technique, rotational resonance NMR spectroscopy, was used to measure a precise (to +/-0.2 A) distance between atomic sites in a substituted imidazo[1,2-a]pyridine, TMPIP, bound to H+/K+-ATPase at its high-affinity site in the intact, native membrane. The structural analysis of the enzyme-inhibitor complex revealed that the flexible moiety of TMPIP adopts a 'syn-type' conformation at its site of action. Hence, the conformation of an inhibitor has been resolved directly under near-physiological conditions, providing a sound experimental basis for rational design of many active compounds of pharmaceutical interest. Chemically restraining the flexible moiety of compounds like TMPIP in the syn-type binding conformation was found to increase activity by over 2 orders of magnitude. Such information is normally only available after extensive synthesis of related compounds and multiple screening approaches.

An old Cornish hand

A wooden upper limb prosthesis, made c.1601, is illustrated with its documentation. It has remained in the possession of the descendants of its original wearer.