Improved deprotection of cysteine-containing peptides in HF

The deprotection of S-4-methylbenzyl-cysteine in HF was studied as a function of acidity and scavengers employed and a highly effective procedure was developed. Under conditions of low acidity which promote S_N2 deprotection of benzyl alcohol-derived protecting groups of amino acid side-chain functionalities, i.e. low HF (HF:DMS, 1:3, v/v), little or no deprotection of S-4-methylbenzyl cysteine was observed. Under conditions of high acidity (90% HF), recovery of cysteine was only 79% using the conventional scavenger, anisole. However a combination of the scavengers p-cresol and p-thiocresol provided nearly quantitative recovery of the cysteine thiol, with the preferred deprotection conditions being HF:p-cresol:p-thiocresol (90:5:5, v/v), 0°C, 1 h. The possibility that the sulfoxide of the protected cysteine thioether was involved in cysteine side reactions was investigated. The formation of the sulfoxide was found to be low (0.15% per residue added) under standard solid-phase peptide synthesis conditions. Since the sulfoxide derivative was resistant to deprotection in high HF, two methods for the reduction of the molecule to the thioether were developed. One method involved the reduction of the sulfoxide in HF at intermediate acidity levels (HF:DMS, 40:60, v/v), 0°, 4h. The other method involved a mixture of TFA, DMS and CH₂Cl₂ (45:10:45, v/v) containing (Et)₄ NCl ? H₂O (50 equiv. per cysteine residue) which efficiently reduced both free and resin-bound S-4-methylbenzyl cysteine sulfoxide (t_1/2= 35 min). Both methods also reduced methionine sulfoxide to methionine.     

Benign transient hyperphosphatasaemia associated with adenovirus infection

: Benign transient hyperphosphatasaemia in early childhood is a harmless biochemical abnormality which is not commonly known to paediatricians. We describe a typical case in a young child and provide further evidence to support a viral aetiology.     

Hyaline Membrane Disease and Early Neonatal Aldosterone Metabolism in Infants of Less than 33 Weeks Gestation

ABSTRACT. We studied urine excretion of free and conjugated aldosterone by 12 control infants and 14 infants with hyaline membrane disease (HMD) on the first and seventh days after birth. Both groups had a mean gestational age of 29 weeks. Total urine aldosterone excretion (UAE) and percent excreted as conjugate were similar for both groups on both study days, and did not relate to the severity of respiratory failure in infants with HMD. Sodium intake was higher for infants with HMD on both study days ( p <0.02), but their urine sodium excretion was only significantly ( p <0.01) higher on day 7. For total UAE values >3 nmol/kg/d, there was no significant difference between estimated sodium-potassium exchange by control (22 ± 5 %, n =8) and HMD (31 ± 5 %, n =10) groups. These data suggest that neither the magnitude of excretion of aldosterone in the urine, the ability to conjugate aldosterone nor the degree of relative distal tubular unresponsiveness to aldosterone are related to the severity of pulmonary immaturity in preterm infants.     

Two cases with a C-group ring autosome

Two boys with a C-group ring autosome, one 81/2 and the other 21/2 years old, are described. The older boy, who had microcephaly, muscular hypotonia and poor co-ordination as well as mental and physical retardation, had an additional chromosomal anomaly in the form of a presumed translocation involving a B-group chromosome and a fragment of the C-group autosome from which the ring was derived. The younger boy showed only retardation of mental and physical development. This investigation was supported by U.S. Public Health Service Research Grant no. NB-04662 from the National Institute of Neurological Diseases and Blindness. We are indebted to Dr Lyn Konugres of the Blood Grouping Laboratory, Boston, for the erythrocyte antigen, haptoglobin and transferrin studies. The technical assistance of the Misses Ida Leone, Mary Hauck. Susan Fletcher, Charlotte King, and Mrs Bettina Hirsch is acknowledged.     

PHOTOLABILE MULTI-DETACHABLE p-ALKOXYBENZYL ALCOHOL RESIN SUPPORTS FOR PEPTIDE FRAGMENT OR SEMI-SYNTHESIS

Two photolabile multi-detachable alkoxybenzyl alcohol resins, 2-[4-(oxymethyl)phenoxy]propionyl-resin 4 and 4-[4-(oxymethyl)phenoxymethyl]-3-nitrobenzamidomethyl-resin 5 have been synthesized. Bpoc-peptide attached to resin 4 or 5 when treated with 50% trifluoroacetic acid provided the free, unprotected peptide, but on photolysis gave Bpoc-peptide p-hydroxybenzyl ester. Removal of the p-hydroxybenzyl ester in aqueous base or by oxidative work up gave a protected Bpoc-peptide suitable for fragment synthesis at its C-terminus. However, methylation of the ester to Bpoc-peptide p-methoxybenzyl ester followed by removal of the Bpoc-group gave a protected peptide p-methoxybenzyl ester suitable for fragment coupling at its N-terminus. The efficacies of these resins were evaluated in the syntheses of a model tetrapeptide and an octapeptide by using N^α-Bpoc-, Fmoc- and Nps-amino acids. The use of 2-thiopyridine with pyridinium hydrochloride as a new and efficient thiolytic reagent for the deprotection of the Nps-group was studied.     

Risk functions for alcohol-related problems in a 1988 US national sample

To assess the relationship of alcohol use and three types of alcohol-related problems (ICD-10 dependence syndrome, work problems and drunk driving), risk curves were developed for average number of drinks per day during last year (volume) and number of days drinking five or more drinks during one day (5 +). Using data from the I98S National Health Interview Alcohol Supplement, risk curves were derived from data on 22 102 current drinkers who consumed at least 12 drinks in the last year. The emphasis in this analysis was on the proportion of drinkers at lower levels reporting different types of problems. The results indicate that even at lower levels of drinking (volume averaging one or fewer drinks/day) there is considerable risk for drunk driving and less risk for work problems and alcohol dependence. The risk for all types of problems at lower and moderate levels of drinking was significantly higher for respondents who had five or more drinks during one day in the last year. These findings underscore the importance of examining risk (physical and social) at lower levels of drinking and for using both overall volume and heavier quantity per occasion drinking measures when assessing risk for any alcohol-related problem.     

Infant weaning and community pharmacy — the pharmacist's perspective

Community pharmacists' awareness of the COMA report on “Weaning and the weaning diet” and their knowledge of its recommendations was assessed in a questionnaire distributed to all (n=81) community pharmacists in the Western Health and Social Services Board in Northern Ireland. Sources of information and adequacy of training on childhood nutritional issues were determined. A knowledge score was computed for each pharmacist depending on their responses to questions based on key issues in the COMA report. Completed questionnaires were returned by 48 pharmacists (59 per cent). The COMA report had been read by 14.5 per cent of respondents while 12.5 per cent knew of its recommendations. Others had heard of it but not read it (52 per cent) or had never heard of it (21 per cent). The mean knowledge score was 66 per cent (±17.5). Scores ranged from 18 per cent to 90 per cent, indicating wide variability in pharmacists' knowledge of key recommendations for weaning. Only 29 per cent of pharmacists felt that they were adequately trained to give advice on weaning; 50 per cent felt that they did not have sufficient knowledge and 21 per cent were unsure. Pharmacists indicated that, on average, parents approached them weekly about a weaning topic, which emphasises the need for them to be well informed about current weaning recommendations.     

Solid phase synthesis of the protected 43–55 tridecapeptide of the heavy chain of myeloma immunoglobin M603, employing cyclohexyl ester protection for glutamic acid

A protected tridecapeptide of the sequence Boc-Lys(2ClZ)-Arg(Tos)-Leu-Glu(OcHex)-Trp(For)-Ile-Ala-Ala-Ser(Bzl)-Arg(Tos)-Asn-Lys(2ClZ)-Gly-OH, representing residues 43–55 of the variable region of the heavy chain of mouse myeloma protein M603, was synthesized. It was assembled by a stepwise solid phase method designed to give a fully protected peptide in high yield and purity with minimal side reactions. Thus, the peptide chain was attached as an α-methyl phenacyl ester to a 2-bromopropionyl-resin. After the synthesis the protected peptide fragment was obtained in 89% yield by photolytic cleavage from the resin. The peptide was purified by multiple precipitation and column chromatography. It was shown to be homogeneous by reverse phase high pressure liquid chromatography, and it had the correct amino acid composition and sequence. In the course of this work it was shown that tert.-butyloxycarbonyl-amino acids caused the formation of significant amounts of pyrrolidone carboxylic acid residues during the coupling reaction when a γ-benzyl glutamyl residue was NH₂-terminal. Other weak-acid additives also caused this chain terminating side reaction. The cyclization was markedly suppressed by protection of the glutamyl side chain as a cyclohexyl ester. With this protecting group, no evidence of pyrrolidone carboxylic acid formation could be detected in the tridecapeptide 43–55.