Gareth Llewellyn

Osteological, biomolecular and geochemical examination of an early anglo-saxon case of lepromatous leprosy.

We have examined a 5th to 6th century inhumation from Great Chesterford, Essex, UK. The incomplete remains are those of a young male, aged around 21–35 years at death. The remains show osteological evidence of lepromatous leprosy (LL) and this was confirmed by lipid biomarker analysis and ancient DNA (aDNA) analysis, which provided evidence for both multi-copy and single copy loci from the Mycobacterium leprae genome. Genotyping showed the strain belonged to the 3I lineage, but the Great Chesterford isolate appeared to be ancestral to 3I strains found in later medieval cases in southern Britain and also continental Europe. While a number of contemporaneous cases exist, at present, this case of leprosy is the earliest radiocarbon dated case in Britain confirmed by both aDNA and lipid biomarkers. Importantly, Strontium and Oxygen isotope analysis suggest that the individual is likely to have originated from outside Britain. This potentially sheds light on the origins of the strain in Britain and its subsequent spread to other parts of the world, including the Americas where the 3I lineage of M. leprae is still found in some southern states of America.

Utilising light-emitting diodes of specific narrow wavelengths for the optimization and co-production of multiple high-value compounds in Porphyridium purpureum

The effect of specific narrow light-emitting diode (LED) wavelengths (red, green, blue) and a combination of LED wavelengths (red, green and blue - RGB) on biomass composition produced by Porphyridium purpureum is studied. Phycobiliprotein, fatty acids, exopolysaccharides, pigment content, and the main macromolecules composition were analysed to determine the effect of wavelength on multiple compounds of commercial interest. The results demonstrate that green light plays a significant role in the growth of rhodophyta, due to phycobiliproteins being able to harvest green wavelengths where chlorophyll pigments absorb poorly. However, under multi-chromatic LED wavelengths, P. purpureum biomass accumulated the highest yield of valuable products such as eicosapentaenoic acid (∼2.9% DW), zeaxanthin (∼586μgg-1DW), β-carotene (397μgg-1DW), exopolysaccharides (2.05g/L-1), and phycobiliproteins (∼4.8% DW). This increased accumulation is likely to be the combination of both photo-adaption and photo-protection, under the combined specific wavelengths employed.

endo,endo- andexo,exo-Bicyclo[1.1.0]butane-2,4-dimethanol Dimesylate: Synthesis, Structure and Solvolysis

The title compounds endo,endo-9 and exo,exo-9 were prepared from benzvalene. As determined by single-crystal X-ray diffraction, several geometrical parameters of endo,endo-9 are particularly remarkable, namely the large interflap angle of the bicyclo[1.1.0]butane system (128.2°) and the length of the C-1−C-3 bond (151.2 pm). Solvolyses of endo,endo-9 in 60% acetone/water, ethanol and 2,2,2-trifluoroethanol gave rise mainly to cis-5-substituted cyclopent-2-ene-1-methanol mesylates (cis-10, cis-11). Small quantities of the corresponding trans isomers (trans-10,trans-11) suggest a configurational conversion of the intermediate, which is proposed to be the nonclassical pseudoaxial 2-mesyloxymethyl-substituted cyclopent-3-en-1-yl cation (ax-31) formed from endo,endo-9 by heterolytic dissociation accompanied by a Wagner-Meerwein rearrangement. The solvolyses of exo,exo-9 took an entirely different course and afforded nonrearranged products (26, 27) exclusively. This is interpreted in terms of the stereochemical requirements of the Wagner−Meerwein rearrangement, which in the case of exo,exo-9 would result in a highly strained cation such as 32 or 33. In consequence, the generation of the bicyclobutylcarbinyl cation 34 seems to be the most favourable alternative. This result, together with kinetic data for solvolyses of endo,endo-9 and exo,exo-9, casts doubt on a report on solvolyses of the dimethylbicyclo[1.1.0]but-2-ylcarbinyl tosylates 6.4 Solvolyses of endo,endo-9 in several solvents are about 5 times faster than those of the ditosylate 2 (or the corresponding dimesylate), a less flexible bicyclo[1.1.0]butane derivative. That the solvolysis of exo,exo-9 takes place about 8 times more slowly than endo,endo-9 is interpreted by invoking a weaker σ-participation in the case of the former. In comparison to the stereochemically closely related exo,exo-9, the cyclobutanedimethanol ditosylate 28 solvolyses only 50 times more slowly.

Chlorophosphate solvolyses. Evaluation of third-order rate laws and rate–product correlations for diphenyl phosphorochloridate in aqueous alcohols†

Rate constants and product selectivities for solvolyses of diphenyl phosphorochloridate in aqueous ethanol and methanol have been determined, along with additional kinetic data for solvolyses in acetone–water, D2O, MeOD, 2,2,2-trifluoroethanol–water, and CF3CH2OH–EtOH. Kinetic data for solvolyses of bis(4-chlorophenyl) phosphorochloridate in the above solvents have also been obtained. The results show that these solvolyses have the following features: (i) no evidence for mechanistic changes over the solvent range ethanol to water; (ii) the largest kinetic solvent isotope effect (KSIE in MeOH/MeOD) yet reported for a chloride solvolysis; (iii) large rate decreases in CF3CH2OH-rich solvents, indicating a very high sensitivity to solvent nucleophilicity. The large KSIE and the product selectivities are well explained by the accepted SN2(P) mechanism, extended to incorporate two solvent molecules in the rate-determining step; i.e. reactions are third-order, with one molecule of solvent acting as nucleophile and the other acting as general base. This relatively simple theory accounts well for several important features of these solvolyses (including solvolyses in trifluoroethanol–water and –ethanol), but the third-order rate constants derived from product selectivities lead to calculated first-order rate constants which are not always in agreement with experimental values. The unexpected failure of the rate–product correlation may be due to initial-state effects, reducing values of third-order rate constants as alcohol is added to water.

Kinetic and spectroscopic characterisation of highly reactive methanesulfonates. Leaving group effects for solvolyses and comments on geminal electronic effects influencing SN1 reactivity

Highly reactive methanesulfonates (mesylates, ROMs) have been prepared from 1-phenylethanol, cyclohex-2-en-1-ol, diphenylmethanol and p-methoxybenzyl alcohol by treatment with methane-sulfonyl chloride and triethylamine in dichloro- or trichloro-methane at –20 to 0 °C. The mesylates, characterised in solution by 1H and 13C NMR at –20 °C, were obtained in satisfactory purity (ca. 95 %) in cold solutions but they decomposed by reaction with chloride, triethylamine or the parent alcohol. Rate constants for solvolyses in aqueous acetone and aqueous ethanol have been determined by a fast response conductimetric method. Product selectivities for solvolyses of p-methoxybenzyl mesylate in aqueous ethanol and methanol at 0 °C have been determined by HPLC. From additional new or literature kinetic data for solvolyses of corresponding bromides, chlorides and p-nitrobenzoates (OPNB), Br/Cl, OMs/Br and OMs/OPNB rate ratios were calculated; the results are consistent with electronic effects stabilising the carbocationic transition states and increasing OMs/Br rate ratios for these SN1 solvolyses; none of the evidence supports a geminal electronic effect on Br/Cl rate ratios (e.g. caused by stabilisation of the initial state in p-methoxybenzyl chloride). Steric effects on ester/halide rate ratios for solvolyses of tertiary substrates are confirmed. Relative rates over a 1016 range for ester and halide leaving groups are evaluated for solvolyses of 1-phenylethyl substrates in 80 % ethanol–water, updating previous work by Noyce et al. (1972).

Limitations of the transition-state variation model. Part 3. Solvolyses of electron-rich benzenesulphonyl chlorides

Rate constants for solvolyses of 4-methoxy-2,6-dimethylbenzenesulphonyl chloride 3(Z = OMe) and of 4-methyl- and 4-methoxybenzenesulphonyl chlorides 4(Z = Me and OMe) are reported for aqueous binary mixtures with acetone, ethanol and methanol. Some additional rate constants are reported for aqueous acetonitrile and dioxane mixtures, as well as product selectivities (S) in alcohol–water mixtures. For each binary mixture, rates of solvolyses of 3(Z = OMe)vs. YCl or Y are approximately bilinear. As water is added to alcohol, S values for solvolyses of 3(Z = OMe) pass through a maximum and for solvolyses of 4-methoxybenzenesulphonyl chloride 4(Z = OMe) the position of the maximum shifts to more aqueous media. For solvolyses of 4-methylbenzenesulphonyl chloride 4(Z = Me), S values are shifted such that they reach a plateau rather than a maximum, and the rate–rate profiles with YCl are approximately linear rather than bilinear. All of the rate–rate profiles show ‘dispersion’ into separate correlations for the various binary mixtures. These substituent effects follow the same trends as corresponding solvolyses of benzoyl chloride and strengthen recent proposals that solvolyses of 3(Z = Me) proceed via competing (dual) reaction channels.

Morphological and biomolecular evidence for tuberculosis in 8th century AD skeletons from Bélmegyer-Csömöki domb, Hungary

Macromorphological analysis of skeletons, from 20 selected graves of the 8th century AD Bélmegyer-Csömöki domb, revealed 19 cases of possible skeletal tuberculosis. Biomolecular analyses provided general support for such diagnoses, including the individual without pathology, but the data did not show coherent consistency over the range of biomarkers examined. Amplification of ancient DNA fragments found evidence for the Mycobacterium tuberculosis complex DNA only in five graves. In contrast, varying degrees of lipid biomarker presence were recorded in all except two of the skeletons, though most lipid components appeared to be somewhat degraded. Mycobacterial mycolic acid biomarkers were absent in five cases, but the weak, possibly degraded profiles for the remainder were smaller and inconclusive for either tuberculosis or leprosy. The most positive lipid biomarker evidence for tuberculosis was provided by mycolipenic acid, with 13 clear cases, supported by five distinct possible cases. Combinations of mycocerosic acids were present in all but three graves, but in one case a tuberculosis-leprosy co-infection was indicated. In two specimens with pathology, no lipid biomarker evidence was recorded, but one of these specimens provided M. tuberculosis complex DNA fragments.

Chiral analysis of synthetic peptides: high performance liquid chromatography of diastereoisomeric carbamoyl esters derived from N-terminal cleavage

A cleavage routine for chiral analysis has revealed that the N-terminal residue in model dipeptides, after derivatisation with a chiral isocyanate reagent, can be cleaved off as the N-carbamoyl ester under relatively mild conditions (MeOH/SOCl2/60 °C for 3 h) free from inherent problems of racemisation. The diastereoisomeric carbamoyl amino acid esters produced can be separated and identified by HPLC. The methodology has been optimised for a number of representative amino acids, including tyrosine, histidine, methionine and tryptophan which have side-functions capable of complicating the procedure.