No skin off your back: the sampling and extraction of sebum for metabolomics.

INTRODUCTION: Sebum-based metabolomics (a subset of "sebomics") is a developing field that involves the sampling, identification, and quantification of metabolites found in human sebum. Sebum is a lipid-rich oily substance secreted by the sebaceous glands onto the skin surface for skin homeostasis, lubrication, thermoregulation, and environmental protection. Interest in sebomics has grown over the last decade due to its potential for rapid analysis following non-invasive sampling for a range of clinical and environmental applications. OBJECTIVES: To provide an overview of various sebum sampling techniques with their associated challenges. To evaluate applications of sebum for clinical research, drug monitoring, and human biomonitoring. To provide a commentary of the opportunities of using sebum as a diagnostic biofluid in the future. METHODS: Bibliometric analyses of selected keywords regarding skin surface analysis using the Scopus search engine from 1960 to 2022 was performed on 12th January 2023. The published literature was compartmentalised based on what the work contributed to in the following areas: the understanding about sebum, its composition, the analytical technologies used, or the purpose of use of sebum. The findings were summarised in this review. RESULTS: Historically, about 15 methods of sampling have been used for sebum collection. The sample preparation approaches vary depending on the analytes of interest and are summarised. The use of sebum is not limited to just skin diseases or drug monitoring but also demonstrated for other systemic disease. Most of the work carried out for untargeted analysis of metabolites associated with sebum has been in the recent two decades. CONCLUSION: Sebum has a huge potential beyond skin research and understanding how one's physiological state affects or reflects on the skin metabolome via the sebaceous glands itself or by interactions with sebaceous secretion, will open doors for simpler biomonitoring. Sebum acts as a sink to environmental metabolites and has applications awaiting to be explored, such as biosecurity, cross-border migration, localised exposure to harmful substances, and high-throughput population screening. These applications will be possible with rapid advances in volatile headspace and lipidomics method development as well as the ability of the metabolomics community to annotate unknown species better. A key issue with skin surface analysis that remains unsolved is attributing the source of the metabolites found on the skin surface before meaningful biological interpretation.

A randomised controlled trial of energetic activity for depression in young people (READY): a multi-site feasibility trial protocol.

BACKGROUND: Prevalence of depression is increasing in young people, and there is a need to develop and evaluate behavioural interventions which may provide benefits equal to or greater than talking therapies or pharmacological alternatives. Exercise could be beneficial for young people living with depression, but robust, large-scale trials of effectiveness and the impact of exercise intensity are lacking. This study aims to test whether a randomised controlled trial (RCT) of an intervention targeting young people living with depression is feasible by determining whether it is possible to recruit and retain young people, develop and deliver the intervention as planned, and evaluate training and delivery. METHODS: The design is a three-arm cluster randomised controlled feasibility trial with embedded process evaluation. Participants will be help-seeking young people, aged 13-17 years experiencing mild to moderate low mood or depression, referred from three counties in England. The intervention will be delivered by registered exercise professionals, supported by mental health support workers, twice a week for 12 weeks. The three arms will be high-intensity exercise, low-intensity exercise, and a social activity control. All arms will receive a 'healthy living' behaviour change session prior to each exercise session and the two exercise groups are energy matched. The outcomes are referral, recruitment, and retention rates; attendance at exercise sessions; adherence to and ability to reach intensity during exercise sessions; proportions of missing data; adverse events, all measured at baseline, 3, and 6 months; resource use; and reach and representativeness. DISCUSSION: UK National Health Service (NHS) policy is to provide young people with advice about using exercise to help depression but there is no evidence-based exercise intervention to either complement or as an alternative to medication or talking therapies. UK National Institute for Health and Care Excellence (NICE) guidelines suggest that exercise can be an effective treatment, but the evidence base is relatively weak. This feasibility trial will provide evidence about whether it is feasible to recruit and retain young people to a full RCT to assess the effectiveness and cost-effectiveness of an exercise intervention for depression. TRIAL REGISTRATION: ISRCTN, ISRCTN66452702 . Registered 9 April 2020.

Characterization and source identification of PM2.5 and its chemical and carbonaceous constituents during Winter Fog Experiment 2015-16 at Indira Gandhi International Airport, Delhi.

Data on mass concentration of PM2.5 and its carbonaceous and water soluble inorganic chemical ions were compiled through sampling of PM2.5 at Indira Gandhi International Airport, Delhi during Dec. 16, 2015-Feb. 15, 2016 under Winter Fog Experiment (WIFEX) program of the Ministry of Earth Sciences (MoES) and analysing the samples. The data so generated were interpreted in terms of their variation on different time scales and apportioning their sources. It is found that mass concentration of PM2.5 averaged over the whole period of observation was 198.6±55.6. The concentration of organic carbon (OC) and elemental carbon (EC) was 24.7±9.4 and 11.7±4.7µg/m3 respectively with no any trend of increase or decrease over the observational period. SO42-, Cl- and NO3- dominated over other anions with their overall average concentration 34.0±23.1, 32.7±16.1 and 13.3±8.7µg/m3 respectively. Among cations, NH4+ showed highest concentration with an average value of 21.0±10.6µg/m3. Variation of daily average mass concentration of these parameters over the period of observation matched well with the variation of PM2.5 mass concentration indicating thereby to be the major contributors to the PM2.5 mass. NH4+ mostly occurred as NH4Cl and NH4NO3 and poorly as (NH4)2SO4 or NH4HSO4. H+ ion mostly occurred as H2SO4 and occasionally as HNO3. Carbonaceous aerosols and NO3- were mainly generated from fossil-fuel combustion. NH4+ and anthropogenic Cl- were mostly generated by biomass burning. The source of SO42- was found to be industries and thermal power plants. Continental Ca2+ and Mg2+ originated from thermal power plants and soil dust.

Surface ozone characterization at Larsemann Hills and Maitri, Antarctica.

Data are analyzed in terms of daily average ozone, its diurnal variation and its relation with meteorological parameters like dry bulb temperature (T), wet bulb temperature (Tw), atmospheric pressure and wind speed based on measurement of these parameters at two Indian Antarctic stations (Larsemann Hills, and Maitri) during 28th Indian Scientific Expedition of Antarctica (ISEA) organized during Antarctic summer of the year 2008-09. The work has been carried out to investigate summer time ozone level and its day-to-day and diurnal variability at these coastal locations and to highlight possible mechanism of ozone production and destruction. The result of the analysis indicates that daily average ozone concentration at Larsemann Hills varied from ~13 and ~20ppb with overall average value of ~16ppb and at Maitri, it varied from ~16 and ~21ppb with overall average value of ~18ppb. Photochemistry is found to partially contribute occasionally to the surface layer ozone at both the stations. Lower concentration of ozone at Maitri during beginning of the observational days may be due to destruction of ozone through activated halogens, whereas higher ozone on latter days may be due to photochemistry and advective transport from east to south-east areas. Ozone concentration during blizzard episodes at both the stations is reduced due to slow photochemical production of ozone, its photochemical removal and removal through deposition of ozone molecules on precipitation particles. Diurnal variation of ozone at Larsemann Hills and Maitri has been found to be absent.

Optical spin injection and spin lifetime in Ge heterostructures.

We demonstrate optical orientation in Ge/SiGe quantum wells and study their spin properties. The ultrafast electron transfer from the center of the Brillouin zone to its edge allows us to achieve high spin polarizations and to resolve the spin dynamics of holes and electrons. The circular polarization degree of the direct gap photoluminescence exceeds the theoretical bulk limit, yielding ∼37% and ∼85% for transitions with heavy and light holes states, respectively. The spin lifetime of holes at the top of the valence band is estimated to be ∼0.5 ps and it is governed by transitions between light and heavy hole states. Electrons at the bottom of the conduction band, on the other hand, have a spin lifetime that exceeds 5 ns below 150 K. Theoretical analysis of the spin relaxation indicates that phonon-induced intervalley scattering dictates the spin lifetime of electrons.

A serious drug interaction leading to spontaneous total hyphema.

A 70 year-old diabetic man receiving anti-coagulant therapy (Warfarin) for pulmonary embolism secondary to factor V Leiden deficiency, presented to the hospital for chest pain. After initial evaluation, he was started on aspirin (300 mg) and clopidogrel (300 mg). Three days after he was discharged, he presented with preseptal cellulitis complicating left upper eyelid chalazion. Initially, he was treated with several anti-microbial agents used sequentially. Although, the cellulitis resolved, he developed total hyphema of the left eye. The complication seems to have resulted from a complex interaction amongst anti-microbial agents, Warfarin and anti-platelet agents.

Parental perceptions regarding healthy behaviours for preventing overweight and obesity in young children: a systematic review of qualitative studies.

Evidence is increasingly pointing towards the importance of early life strategies to prevent childhood overweight and obesity. This systematic review synthesizes qualitative research concerning parental perceptions regarding behaviours for preventing overweight and obesity in young children. During May and June 2008, a range of electronic databases were searched and together with lateral searching techniques 21 studies were identified for review. Data extraction and synthesis using thematic content analysis revealed six organizing and 32 finer level themes. These related to child factors, family dynamics, parenting, knowledge and beliefs, extra-familial influences and resources and environment. Themes were mapped to a socioecological model which illustrated how factors at individual, interpersonal, community, organizational and societal levels interact in complex ways to impact on parental perceptions about healthy behaviours for preventing child overweight. Although parents suggested several ideas to promote healthy child weight-related behaviours, many of their views concerned perceived barriers, some of which may be amenable to practical intervention. Furthermore, intergenerational influences on parental health beliefs and knowledge suggest that health promotion strategies may be more effective if directed at the wider family, rather than parents alone. Significantly, many parents believed strategies to promote healthy weight should start early in a child's life.

Early fatherhood: a mapping of the evidence base relating to pregnancy prevention and parenting support.

Teenage pregnancy prevention programmes targeted at young women have received considerable attention from researchers and programme developers. However, to date, relatively limited information is available on preventing teenage fatherhood or improving outcomes for young fathers. A notable gap is concerned with understanding the forms of sexual health programmes that are most effective from the perspective of young men. We conducted a systematic mapping to identify studies involving young men aimed at preventing teenage pregnancy, improving outcomes for teenage fathers or exploring the perspectives of young men around pregnancy and fatherhood. We searched a wide range of electronic databases from January 1996 to August 2008. Three quantitative and 15 qualitative studies were identified, of which nine were UK based. Key themes related to the inappropriateness of current sexual health promotion to respond to the needs of young men. While young men often possessed very similar ideals to young women, existing programmes were problematic when they negatively stereotyped young men and ineffectively addressed models of masculinity or the difficulties young men may have forming meaningful relationships. Further investigations are required on programme development for young men, particularly on sexual health promotion interventions for 'looked-after' young men and those from unstable childhoods.

High-resolution optical coherence tomography demonstration of membranes spanning optic disc pits and colobomas.

OBJECTIVES: To demonstrate the features of optic disc pits and colobomas revealed by high-resolution optical coherence tomography (OCT) and their association with the development of maculopathy. METHODS: Subjects with disc pits or colobomas and no other ocular history underwent full ophthalmic examinations including logMAR visual acuity and contrast sensitivity. Fundus photographs and high-resolution OCT images were obtained. RESULTS: Seven patients were identified with optic disc pits or colobomas aged 25 to 63 years. Five patients had a unilateral optic disc pit, one had a unilateral disc coloboma, and another had bilateral disc colobomas. Apart from one eye with a grossly anomalous disc, vision was logMAR 0.4 or better in all eyes. In three of five eyes without maculopathy, a complete membrane could be identified traversing the optic disc cup that was absent or deficient in the three eyes with maculopathy. One patient with optic disc pit and marked schisis-like separation of the retinal layers throughout the macula was asymptomatic with logMAR visual acuity of 0.0 and normal achromatic contrast sensitivity. CONCLUSIONS: In this small series of patients with optic disc pits or colobomas, it was possible to identify a membrane spanning the optic disc cup, and it is speculated that this may protect against the development of maculopathy. Schisis-like separation of retinal layers can be associated with normal visual function.

Coexistence of squamous cell carcinoma with dermoid cyst of ovary.

A 40-year-old female presented with pain and enlargement of abdomen since last 6 months. A mass was felt over right iliac fossa. Ultrasonography showed partly cystic and solid area in mass arising from ovary. A tooth-like structure was also seen. Dermoid cyst was the diagnosis offered. Laparotomy was performed. Ovarian mass with hair, a tooth and putty-like material was present. Solid white area with thickened wall was found. Histopathology confirmed the findings of dermoid cyst and the thickened area showed squamous cell carcinoma with areas showing keratinous material and giant cell reaction which was also seen at the periphery of tumor areas. Left ovary was normal and no deposits of tumor were seen. Postoperative period was uneventful.

Colloid solutions for fluid resuscitation.

BACKGROUND: Colloids are widely used in the replacement of fluid volume. However doubts remain as to which colloid is best. Different colloids vary in their molecular weight and therefore in the length of time they remain in the circulatory system. Because of this and their other characteristics, they may differ in their safety and efficacy. OBJECTIVES: To compare the effects of different colloid solutions in patients thought to need volume replacement. SEARCH STRATEGY: We searched the Cochrane Injuries Group specialised register, CENTRAL (2007, Issue 1), MEDLINE (1994 to March 2007), EMBASE (1974 to March 2007), and the National Research Register (2007, issue 1). Bibliographies of trials retrieved were searched, and drug companies manufacturing colloids were contacted for information. The search was last updated in March 2007. SELECTION CRITERIA: Randomised and quasi-randomised trials comparing colloid solutions in critically ill and surgical patients thought to need volume replacement. The outcomes measured were death, amount of whole blood transfused, and incidence of adverse reactions. DATA COLLECTION AND ANALYSIS: Two authors independently extracted the data and assessed the quality of the trials. MAIN RESULTS: Seventy trials, with a total of 4375 participants, met the inclusion criteria. Quality of allocation concealment was judged to be adequate in 24 trials and poor or uncertain in the rest. Deaths were obtained in 46 trials. For albumin or PPF versus hydroxyethyl starch (HES) 25 trials (n = 1234) reported mortality. The pooled relative risk (RR) was 1.14 (95% CI 0.91 to 1.43). For albumin or PPF versus gelatin, seven trials (n = 636) reported mortality. The RR was 0.97 (95% CI 0.68 to 1.39). For albumin or PPF versus Dextran four trials (n = 360) reported mortality. The RR was 3.75 (95% CI 0.42 to 33.09). For gelatin versus HES 18 trials (n = 1337) reported mortality and RR was 1.00 (95% CI 0.80 to 1.25). RR was not estimable in the gelatin versus dextran and HES versus dextran groups.Thirty-seven trials recorded the amount of blood transfused, however quantitative analysis was not possible due to skewness and variable reporting. Nineteen trials recorded adverse reactions, but none occurred. AUTHORS' CONCLUSIONS: From this review, there is no evidence that one colloid solution is more effective or safe than any other, although the confidence intervals are wide and do not exclude clinically significant differences between colloids. Larger trials of fluid therapy are needed if clinically significant differences in mortality are to be detected or excluded.

ReCLAIM v2.0: a spreadsheet tool for calculating doses and soil/water radionuclide screening levels for assessment of radioactively contaminated land.

This note describes an electronic spreadsheet tool called ReCLAIM v2.0, developed by Nexia Solutions Ltd. The tool calculates doses to exposure groups for assessment of radioactively contaminated land including UK Nuclear Licensed sites on an individual exposure pathway basis and on a multiple exposure pathway basis constituting various specifiable scenarios. It also calculates soil/water screening levels of individual radionuclides with reference to selected exposure pathways and a dose target, and considers radionuclide additivity. Subject to agreement with a ReCLAIM disclaimer, the tool, with accompanying documentation (User Guide and Verification Report), can be downloaded without cost from the website (www.nexiasolutions.com/reclaim).

Biosensing and drug delivery by polypyrrole.

Conducting polypyrrole is a biological compatible polymer matrix wherein number of drugs and enzymes can be incorporated by way of doping. The polypyrrole, which is obtained as freestanding film by electrochemical polymerization, has gained tremendous recognition as sophisticated electronic measuring device in the field of sensors and drug delivery. In drug delivery the reversing of the potential 100% of the drug can be released and is highly efficient as a biosensor in presence of an enzyme. In this review we discuss the applications of conducting polypyrrole as biosensor for some biomolecules and drug delivery systems.

An association between respiratory function and hip bone mineral density in older men: a cross-sectional study.

The association between respiratory function and bone mineral density (BMD) among women living in the community has been reported previously. We examined the association between forced expiratory volume in 1 s (FEV(1)) and BMD measured at hip using dual-energy X-ray absorptiometry in a group of 947 men (aged 65 to 76 years) recruited from general practice age-sex registers in Cambridge between 1991 and 1995. A positive and significant correlation was seen between FEV(1) and BMD measured at total hip, femoral neck, and trochanter. A unit change (1 l) in FEV(1) was associated with a change of BMD by 0.019, 0.017, and 0.026 g/cm(2) in the total hip, femoral neck, and tochanteric region, respectively. These associations were independent of possible confounding factors such as age, height, weight, smoking habit, major disease prevalence, and medications, which might affect bone metabolism. In categorical analyses, the highest BMD was seen in the highest FEV(1) quartile, while the lowest BMD was seen in the lowest FEV(1) quartile. This pattern was seen in all three skeletal sites and was independent of covariates listed above. Compared with the bottom FEV(1) quartile, mean hip BMDs in the top quartile were 2-3.5% higher. The exact mechanism of this association is not clear to us. One plausible explanation is that respiratory function and bone health both reflect common but as yet unknown determinants.

Biological and conformational study of beta-substituted prolines in MT-II template: steric effects leading to human MC5 receptor selectivity.

To investigate the molecular basis for the interaction of the chi-constrained conformation of melanotropin peptide with the human melanocortin receptors, a series of beta-substituted proline analogs were synthesized and incorporated into the Ac-Nle-C[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 (MT-II) template at the His6 and D-Phe7 positions. It was found that the binding affinities generally diminished as the steric bulk of the p-substituents of the 3-phenylproline residues increased. From (2S, 3R)-3-phenyl-Pro6 to (2S, 3R)-3-(p-methoxyphenyl)-Pro6 analogs the binding affinity decreased 23-fold at the human melanocortin-3 receptor (hMC3R), 17-fold at the hMC4R, and eight-fold at the hMC5R, but selectivity for the hMC5R increased. In addition, the substitution of the D-Phe7 residue with a (2R, 3S)-3-phenyl-Pro resulted in greatly reduced binding affinity (10(3)-10(5)) at these melanocortin receptors. Macromodel's Large Scale Low Mode (LLMOD) with OPLS-AA force field simulations revealed that both MT-II and SHU-9119 share a similar backbone conformation and topography with the exception of the orientation of the side chains of D-Phe7/D-Nal (2')7 in chi space. Introduction of the dihedrally constrained phenylproline analogs into the His6 position (analogs 2-6) caused topographical changes that might be responsible for the lower binding affinities. Our findings indicate that hMC3 and hMC4 receptors are more sensitive to steric effects and conformational constraints than the hMC5 receptor. This is the first example for melanocortin receptor selectivity where the propensity of steric interactions in chi space of beta-modified Pro6 analogs of MT-II has been shown to play a critical role for binding as well as bioefficacy of melanotropins at hMC3 and hMC4 receptors, but not at the hMC5 receptor.

Green tea (Camellia sinensis) protects against selenite-induced oxidative stress in experimental cataractogenesis.

Cataract is the leading cause of blindness worldwide. It is a multifactorial disease primarily associated with oxidative stress produced by free radicals. The protection offered by various antioxidants in cataract development is well established. Polyphenolic compounds present in green tea (Camellia sinensis) are reported to possess antioxidant property in various pathological conditions. The present study was undertaken to evaluate the anticataract potential of green tea leaf (GTL) extract in the development of lens opacification. Enucleated rat lenses were randomly divided into normal, control and treated groups and incubated for 24 h at 37 degrees C. Oxidative stress was induced by sodium selenite in the culture medium of the two groups (except the normal group). The medium of the treated group was additionally supplemented with GTL extract. After incubation, lenses were subjected to glutathione and malondialdehyde estimation. Enzyme activity of superoxide dismutase, catalase and glutathione peroxidase was also measured in different sets of the experiment. In vivo cataract was induced in 9-day-old rat pups of both control and treated groups by a single subcutaneous injection of sodium selenite. The treated pups were injected GTL extract intraperitoneally prior to selenite challenge and continued for 2 consecutive days thereafter. Cataract incidence was evaluated on 16th postnatal day by slit lamp examination. There was positive modulation of biochemical parameters in the organ culture study. Green tea was also found to reduce the incidence of selenite cataract in vivo. The results suggest that green tea possesses significant anticataract potential and acts primarily by preserving the antioxidant defense system.

An association between respiratory function and bone mineral density in women from the general community: a cross sectional study.

Respiratory function has been associated with bone mineral density (BMD) in patients with respiratory diseases. We examined the relationship between bone density measured at the hip and respiratory function in women from the general community. A total of 4830 women aged 45-76 years were recruited from general practice age-sex registers in Cambridge between 1991 and 1995. At baseline survey, data collection included health questionnaires, measures of anthropometry, respiratory function, as well as bone mineral density BMD measured using dual energy X ray absorptiometry. BMD at total hip, femoral neck and trochanter significantly and positively correlated with FEV(1). This association was independent of age, weight, height, smoking habit, history of respiratory diseases, corticosteroids and use of hormone replacement therapy. After adjustment for these factors, an increase in FEV(1) of 1 l/s was associated with 0.026, 0.021 and 0.026g/cm(2) increase in bone mineral density at total hip, femoral neck and trochanter respectively. The association was consistent and similar in magnitude among current smokers and current non-smokers and across all age groups. The magnitude of the association was comparable to that associated with an age difference of 6 years or weight difference of 5 kg. Women in the bottom compared to top quartile of respiratory function had about double the risk of low bone density independent of other factors. Respiratory function measured using FEV(1) is positively and independently related to BMD in these middle-aged and older women across the whole normal distribution of these physiologic measures. This may reflect underlying common determinants such as physical activity. Even in healthy women, respiratory function may be a marker for women at increased risk of osteoporosis and associated fractures.

Dehydroepiandrosterone sulfate and mortality in elderly men and women.

Dehydroepiandrosterone sulfate levels have been inversely related with cardiovascular mortality in men, but findings have been inconsistent, and there are few data in women. We examined the relationship between baseline circulating dehydroepiandrosterone sulfate levels and subsequent all-cause and cardiovascular mortality in 963 men and 1171 women, 65-76 yr old, surveyed in 1991-1995, and followed up until August 2000 (when 296 deaths had occurred). All-cause and cardiovascular disease mortality rates were highest in the lowest dehydroepiandrosterone sulfate quartile in men; and thereafter, rates did not differ significantly in the upper three quartiles. This pattern remained after excluding those with previous history of cardiovascular disease and, in multivariate analyses, was independent of age, cigarette smoking habit, systolic blood pressure, body mass index, blood cholesterol, and steroid use. There was no significant association of dehydroepiandrosterone sulfate and mortality in women. The multivariate adjusted relative risks for all-cause mortality by sex-specific increasing quartile of dehydroepiandrosterone sulfate were 1.00, 0.66 (95% confidence interval, 0.44-1.01), 0.70 (0.46-1.07), 0.73 (0.48-1.10), respectively, for men and 1.00, 0.71 (95% confidence interval, 0.41-1.24), 0.97 (0.58-1.62), and 1.14 (0.69-1.88), respectively, for women. In older men and women, there is no consistent relationship between dehydroepiandrosterone sulfate and all-cause or cardiovascular mortality. The highest mortality rates were observed in the lowest quartile in men, but the highest rates were in the highest quartile in women.

Development of potent glucagon antagonists: structure-activity relationship study of glycine at position 4.

We examined the functional role of glycine at position 4 in the potent glucagon antagonist [desHis(1), Glu(9)]glucagon amide, by substituting the L- and D-enantiomers of alanine and leucine for Gly(4) in this antagonist. The methyl and isobutyl side-chain substituents were introduced to evaluate the preference shown by the glucagon receptor, if any, for the orientation of the N-terminal residues. The L-amino acids demonstrated only slightly better receptor recognition than the D-enantiomers. These results suggest that the Gly(4) residue in glucagon antagonists may be exposed to the outside of the receptor. The enhanced binding affinities of analogs 1 and 3 compared with the parent antagonist, [desHis(1), Glu(9)]glucagon amide, may have resulted from the strengthened hydrophobic patch in the N-terminal region and/or the increased propensity for a helical conformation due to the replacement of alanine and leucine for glycine. Thus, as a result of the increased receptor binding affinities, antagonist activities of analogs 1-4 were increased 10-fold compared with the parent antagonist, [desHis(1), Glu(9)]glucagon amide. These potent glucagon antagonists have among the highest pA(2) values of any glucagon analogs reported to date.

A new approach to search for the bioactive conformation of glucagon: positional cyclization scanning.

In search for the bioactive conformation of glucagon, "positional cyclization scanning" was used to determine secondary structures of glucagon required for maximal interaction with the glucagon receptor. Because glucagon is flexible in nature, its bioactive conformation is not known except for an amphiphilic helical conformation at the C-terminal region. To understand the conformational requirement for the N-terminal region that appears to be essential for signal transduction, a series of glucagon analogues conformationally constrained by disulfide or lactam bridges have been designed and synthesized. The conformational restrictions via disulfide bridges between cysteine i and cysteine i + 5, or lactam bridges between lysine i and glutamic acid i + 4, were applied to induce and stabilize certain corresponding secondary structures. The results from the binding assays showed that all the cyclic analogues with disulfide bridges bound to the receptor with significantly reduced binding affinities compared to their linear counterparts. On the contrary, glucagon analogues containing lactam bridges, in particular, c[Lys(5), Glu(9)]glucagon amide (10) and c[Lys(17), Glu(21)]glucagon amide (14), demonstrated more than 7-fold increased receptor binding affinities than native glucagon. These results suggest that the bioactive conformation of glucagon may adopt a helical conformation at the N-terminal region as well as the C-terminal region, which was not evident from earlier biophysical studies of glucagon.