Barriers to HIV testing as reported by individuals newly diagnosed with HIV infection in Sweden.

Despite the availability of free and anonymous HIV testing almost 60% of Swedish patients are diagnosed late. Identifying predictors of different types of barriers could inform policy makers and health care of interventions to increase testing where needed. This cross-sectional study aimed to describe and analyze barriers to HIV testing as reported by Swedish patients newly diagnosed with HIV infection. N = 285 patients completed the 18-item Barriers to HIV Testing Scale - Karolinska Version. Descriptive analysis and logistic regressions were performed to assess the prevalence of barriers and to identify predictors for the different investigated barriers. Barriers to testing were reported by 60%. Approximately 67% of patients originating from Sweden, 50% from Sub-Saharan Africa and 75% from Eastern European/East Asian countries reported barriers. Patients who were younger and patients who self-initiated HIV testing, had greater odds of reporting a barrier than older individuals and those who were offered a test through screening or by a healthcare professional. To counteract barriers that still exist on an individual level, healthcare-initiated HIV testing could be offered more broadly and information about risks for transmission and effectiveness of HIV treatment still needs to be disseminated among both people born in Sweden and different migrant groups.

Sexual dysfunction and fertility-related distress in young adults with cancer over 5 years following diagnosis: study protocol of the Fex-Can Cohort study.

BACKGROUND: There is a lack of firm knowledge regarding sexual problems and fertility-related distress in young adults following a diagnosis with cancer. Establishing such understanding is essential to identify patients in need of specific support and to develop cancer care accordingly. This study protocol describes the Fex-Can Cohort study, a population-based prospective cohort study investigating sexual dysfunction and fertility-related distress in young adults diagnosed with cancer in Sweden. The primary objective of the study is to determine the prevalence and predictors of sexual dysfunction and fertility-related distress following a cancer diagnosis in young adulthood compared to prevalence rates for the general population. Further aims are to investigate the trajectories of these issues over time, the co-existence between sexual dysfunction and fertility-related distress, and the relation between these issues and body image, anxiety and depression, health-related quality of life, self-efficacy related to sexuality and fertility, and fertility-related knowledge. METHODS: Participants in the Fex-Can Cohort will be identified via the Swedish National Quality Registries for Brain Tumors, Breast Cancer, Gynecological Oncology, Lymphoma, and Testicular Cancer. All patients diagnosed at the ages of 18-39, during a period of 18 months, will be invited to participate. Established instruments will be used to measure sexual function (PROMIS SexFS), fertility-related distress (RCAC), body image (BIS), anxiety and depression (HADS), and health-related quality of life (QLQ-C30); Self-efficacy and fertility-related knowledge will be assessed by study-specific measures. The survey will be administered to participants at baseline (approximately 1.5 year after diagnosis) and at 3 and 5 years post-diagnosis. Registry data will be used to collect clinical variables. A comparison group of 2000 young adults will be drawn from the Swedish population register (SPAR) and subsequently approached with the same measures as the cancer group. DISCUSSION: The study will determine the prevalence and predictors of sexual dysfunction and fertility-related distress in young men and women with cancer. The findings will form a basis for developing interventions to alleviate sexual problems and fertility-related distress in young adults with cancer in the short and long term. TRIAL REGISTRATION: This is an observational cohort study and clinical trial registration was therefore not obtained.

A web-based psycho-educational intervention (Fex-Can) targeting sexual dysfunction and fertility-related distress in young adults with cancer: study protocol of a randomized controlled trial.

BACKGROUND: This study protocol describes the clinical trial of the Fex-Can intervention, a web-based self-help program targeting sexual dysfunction and fertility-related distress. The psycho-educational intervention has been developed in collaboration with young patients with cancer and shown to be feasible. The primary objective is to determine whether the Fex-Can intervention, provided in addition to standard care, is superior to standard care in terms of reduction of sexual dysfunction and fertility-related distress directly after end of the 12-week program. The trial also aims to determine whether the intervention has an effect on the secondary outcomes including health-related quality of life, anxiety, depression, body image, fertility knowledge, and self-efficacy related to sexuality and fertility. METHODS: The trial has an randomized clinical trial (RCT) design with two parallel arms. The active groups receive either the version of the Fex-Can intervention targeting sexual problems or the version targeting fertility-related distress. Control groups receive standard care. Primary outcomes will be sexual function assessed with the Patient-Reported Outcomes Measurement Information System® Sexual Function and Satisfaction measure version 2.0 (SexFS) and fertility-related distress assessed with the Reproductive Concerns After Cancer scale (RCAC). The effect of the intervention will be evaluated directly after end of the program. Primary and secondary outcomes will also be assessed at the short- (12 weeks after end of program) and long-term (20 and 44 months after end of program) follow-up. At least 64 completers will be needed in each arm (total n = 256) to achieve adequate statistical power in the analyses. In order to increase the understanding of how the intervention brings about a possible change, semi-structured interviews will additionally be conducted with a purposeful sample shortly after completion of the intervention. DISCUSSION: If the Fex-Can intervention proves to be efficacious the necessary steps will be taken to implement it in routine care for young adults diagnosed with cancer. Healthcare could thereby be provided with an easily accessible, cost-effective intervention to offer to young adults suffering from fertility-related distress or sexual problems. TRIAL REGISTRATION: ISRCTN36621459 . Registered 25 January 2016.

Sexual Dysfunction and Reproductive Concerns in Young Men Diagnosed With Testicular Cancer: An Observational Study.

INTRODUCTION: The survival rates for testicular cancer are excellent; still, there is a lack of knowledge regarding important survivorship issues, such as sexual dysfunction and reproductive concerns. AIM: The aim of this study was to investigate the prevalence and predictors of sexual dysfunction and reproductive concerns and the potential association between these issues in young men ∼2 years after a diagnosis of testicular cancer. METHODS: Data were collected from 111 men (response rate = 50%) diagnosed with testicular cancer at age 16-39. Patients were identified via the Swedish National Quality Registry for Testicular Cancer and approached with a survey, including standardized measures of sexual function, reproductive concerns, body image, and health-related quality of life. The survey was sent to participants approximately 2 years after their cancer diagnosis. Clinical variables were collected from the registry. Predictors were identified by multivariable linear regression analyses. MAIN OUTCOME MEASURES: The main outcomes were sexual function, assessed with the Patient-Reported Outcomes Measurement Information System Sexual Function and Satisfaction measure version 2.0, and reproductive concerns, assessed with the Reproductive Concerns After Cancer scale. RESULTS: Sexual dysfunction was reported by 26% of men, and a high level of reproductive concerns was reported by 28%. Lower satisfaction with sex life was associated with older age (ß = -0.41), negative body image (ß = -0.42), not having a partner (ß = 4.8), and dissatisfaction with sex life before cancer (ß = 8.31). Negative body image was associated with reproductive concerns in the dimensions of fertility potential (ß = 0.06), partner disclosure (ß = 0.08), and child's health (ß = 0.07), whereas having had fertility preservation predicted higher levels of concerns with regard to personal health (ß = 0.52) and achieving pregnancy (ß = 0.53). Clinical variables did not predict either sexual function or reproductive concerns. CLINICAL IMPLICATIONS: Our results show that the majority of young men diagnosed with testicular cancer do not report sexual dysfunction or reproductive concerns 2 years after diagnosis. A sizeable minority, however, does report dysfunction or reproductive concerns, which should be recognized in the follow-up care of this population. STRENGTHS & LIMITATIONS: A strength of the study is the use of high-quality registry data and validated instruments. The lack of Swedish norms for sexual function and reproductive concerns is a possible limitation. CONCLUSION: A subgroup of young men treated for testicular cancer report sexual dysfunction or reproductive concerns approximately 2 years after diagnosis. Factors associated with these issues seem to mainly be psychological, rather than medical, nature. Ljungman L, Eriksson LE, Flynn KE, et al. Sexual Dysfunction and Reproductive Concerns in Young Men Diagnosed With Testicular Cancer: An Observational Study. J Sex Med 2019;16:1049-1059.

'Will I be able to have a baby?' Results from online focus group discussions with childhood cancer survivors in Sweden.

STUDY QUESTION: What do adolescent and young adult survivors of childhood cancer think about the risk of being infertile? SUMMARY ANSWER: The potential infertility, as well as the experience of having had cancer, affects well-being, intimate relationships and the desire to have children in the future. WHAT IS KNOWN ALREADY: Many childhood cancer survivors want to have children and worry about possible infertility. STUDY DESIGN, SIZE, DURATION: For this qualitative study with a cross-sectional design, data were collected through 39 online focus group discussions during 2013. PARTICIPANTS/MATERIALS, SETTING, METHODS: Cancer survivors previously treated for selected diagnoses were identified from The Swedish Childhood Cancer Register (16-24 years old at inclusion, ≥5 years after diagnosis) and approached regarding study participation. Online focus group discussions of mixed sex (n = 133) were performed on a chat platform in real time. Texts from the group discussions were analysed using qualitative content analysis. MAIN RESULTS AND THE ROLE OF CHANCE: The analysis resulted in the main category Is it possible to have a baby? including five generic categories: Risk of infertility affects well-being, Dealing with possible infertility, Disclosure of possible infertility is a challenge, Issues related to heredity and Parenthood may be affected. The risk of infertility was described as having a negative impact on well-being and intimate relationships. Furthermore, the participants described hesitation about becoming a parent due to perceived or anticipated physical and psychological consequences of having had cancer. LIMITATIONS, REASONS FOR CAUTION: Given the sensitive topic of the study, the response rate (36%) is considered acceptable. The sample included participants who varied with regard to received fertility-related information, current fertility status and concerns related to the risk of being infertile. WIDER IMPLICATIONS OF THE FINDINGS: The results may be transferred to similar contexts with other groups of patients of childbearing age and a risk of impaired fertility due to disease. The findings imply that achieving parenthood, whether or not with biological children, is an area that needs to be addressed by health care services. STUDY FUNDING/COMPETING INTERESTS: The study was financially supported by The Cancer Research Foundations of Radiumhemmet, The Swedish Childhood Cancer Foundation and the Doctoral School in Health Care Science, Karolinska Institutet. The authors report no conflicts of interest.

An exploration of patient-reported symptoms in systemic lupus erythematosus and the relationship to health-related quality of life.

OBJECTIVE: The aim of this study was to explore the most distressing symptoms of systemic lupus erythematosus (SLE) and determine how these relate to health-related quality of life (HRQoL), anxiety/depression, patient demographics, and disease characteristics (duration, activity, organ damage). METHODS: In a cross-sectional study, patients with SLE (n = 324, age 18-84 years) gave written responses regarding which SLE-related symptoms they experienced as most difficult. Their responses were categorized. Within each category, patients reporting a specific symptom were compared with non-reporters and analysed for patient demographics, disease duration, and results from the following questionnaires: the Medical Outcomes Study 36-item Short Form Health Survey (SF-36), the Hospital Anxiety and Depression Scale (HADS), the Systemic Lupus Activity Measure (SLAM), the SLE Disease Activity Index (SLEDAI), and the Systemic Lupus International Collaboration Clinics/American College of Rheumatology (SLICC/ACR) damage index. RESULTS: Twenty-three symptom categories were identified. Fatigue (51%), pain (50%), and musculoskeletal distress (46%) were most frequently reported. Compared with non-reporters, only patients reporting fatigue showed a statistically significant impact on both mental and physical components of HRQoL. Patients with no present symptoms (10%) had higher HRQoL (p < 0.001) and lower levels of depression (p < 0.001), anxiety (p < 0.01), and disease activity (SLAM) (p < 0.001). CONCLUSION: Fatigue, pain, or musculoskeletal distress dominated the reported symptoms in approximately half of the patients. Only patients reporting fatigue scored lower on both mental and physical aspects of HRQoL. Our results emphasize the need for further support and interventions to ease the symptom load and improve HRQoL in patients with SLE. Our findings further indicate that this need is particularly urgent for patients with symptoms of pain or fatigue.

Relevance of the N-terminal NLS-like sequence of the prion protein for membrane perturbation effects.

We investigated the nuclear localization-like sequence KKRPKP, corresponding to the residues 23-28 in the mouse prion protein (mPrP), for its membrane perturbation activity, by comparing effects of two mPrP-derived peptides, corresponding to residues 1-28 (mPrPp(1-28)) and 23-50 (mPrPp(23-50)), respectively. In erythrocytes, mPrPp(1-28) induced approximately 60% haemoglobin leakage after 30 min, whereas mPrPp(23-50) had negligible effects. In calcein-entrapping, large unilamellar vesicles (LUVs), similar results were obtained. Cytotoxicity estimated by lactate dehydrogenase leakage from HeLa cells, was found to be approximately 12% for 50 microM mPrPp(1-28), and approximately 1% for 50 microM mPrPp(23-50). Circular dichroism spectra showed structure induction of mPrPp(1-28) in the presence of POPC:POPG (4:1) and POPC LUVs, while mPrPp(23-50) remained a random coil. Membrane translocation studies on live HeLa cells showed mPrPp(1-28) co-localizing with dextran, suggesting fluid-phase endocytosis, whereas mPrPp(23-50) hardly translocated at all. We conclude that the KKRPKP-sequence is not sufficient to cause membrane perturbation or translocation but needs a hydrophobic counterpart.

Health-related quality of life in homo- and bisexual men attending a sexually transmitted disease clinic in Sweden.

Men who have sex with men (MSM) have an increased risk of contracting sexually transmitted diseases (STDs) and HIV. Studies of their health-related quality of life (HRQL) are uncommon, though such studies may provide additional knowledge that is of interest in counselling and care. The HRQL in MSM attending a clinic for STD- and HIV testing in Stockholm, Sweden, was investigated in 1996 and 2004, measured by means of the Swedish Health-Related Quality of Life questionnaire. The results were compared with those for men from a general Swedish population sample and with HIV-infected men. The HIV-negative MSM had significantly worse emotional wellbeing, satisfaction with family life, relation to their partner and general health perception, and better physical HRQL compared with the general Swedish population. There were no differences in the emotional and family dimensions between HIV-infected and HIV-negative MSM, but the HIV-negative group scored at a higher level in respect of their physical and general health than the HIV-infected group. No apparent differences over time were seen in the HIV-negative group. This study shows that psychosocial HRQL is lower for MSM than for a general male population sample, which calls for increased attention in the care of MSM patients.

Membrane perturbation effects of peptides derived from the N-termini of unprocessed prion proteins.

Peptides derived from the unprocessed N-termini of mouse and bovine prion proteins (mPrPp and bPrPp, respectively), comprising hydrophobic signal sequences followed by charged domains (KKRPKP), function as cell-penetrating peptides (CPPs) with live cells, concomitantly causing toxicity. Using steady-state fluorescence techniques, including calcein leakage and polarization of a membrane probe (diphenylhexatriene, DPH), as well as circular dichroism, we studied the membrane interactions of the peptides with large unilamellar phospholipid vesicles (LUVs), generally with a 30% negative surface charged density, comparing the effects with those of the CPP penetratin (pAntp) and the pore-forming peptide melittin. The prion peptides caused significant calcein leakage from LUVs concomitant with increased membrane ordering. Fluorescence correlation spectroscopy (FCS) studies of either rhodamine-entrapping (REVs) or rhodamine-labeled (RLVs) vesicles, showed that addition of the prion peptides resulted in significant release of rhodamine from the REVs without affecting the overall integrity of the RLVs. The membrane leakage effects due to the peptides had the following order of potency: melittin>mPrPp>bPrPp>pAntp. The membrane perturbation effects of the N-terminal prion peptides suggest that they form transient pores (similar to melittin) causing toxicity in parallel with their cellular trafficking.

On the shape of human red blood cells interacting with flat artificial surfaces--the 'glass effect'.

The morphology of the human red blood cell (RBC) contained between two flat artificial surfaces has been investigated. Shape transformation from the discocytic into various crenated (echinocytic) states was not caused solely by glass ('glass effect'). Various organic polymers, and mica, were effective, provided the distance (0.1 mm) between the two surfaces was carefully controlled. The discocytic state could only be preserved using moderately hydrophobic glass, extensive dimethylsilylation induced stomatocytes. With washed blood samples crenation occurred in a potassium chloride medium and in the presence of EDTA. Temperature-dependent transformation in the shape of human erythrocytes occurred between two glass surfaces 0.1 mm apart, e.g., in a hemacytometer. With cells in blood diluted directly 200-times with isotonic saline crenation appeared at 32-36 degrees C. A sphero-echinocytic state prevailed at 34 degrees C and outside the temperature range of 32-36 degrees C the RBCs retained the shape of a biconcave disk. Cells responding to the 'glass effect' even at temperatures below the transition region did not respond further at elevated temperatures. The 'glass effect' was found to be dependent on the RBC concentration (hematocrit). Raising this concentration reversibly decreased the degree of crenation. The amount of endogenous albumin present was estimated to be insufficient to cover the exposed glass surfaces with a protein monolayer. With washed cells over a wide concentration range, approximately the same total amount of albumin (serum) had to be present to avoid crenation, as long as observation was performed at a fixed low cell concentration. The effect of albumin was not abolished by gamma-globulin or anti-human albumin IgG. The discocyte-stabilizing influence of albumin is discussed.

The interaction of various lanthanide ions and some anions with phosphatidylcholine vesicle membranes. A 31P NMR study of the surface potential effects.

The interaction of various lanthanide ions with vesicles of phosphatidylcholine from egg yolk has been followed by 31P NMR at 30 degrees C. From known magnetic properties of these ions, separation of the paramagnetic shift into a pure contact and a pseudo-contact part was carried out. Binding curves for the contact contribution (F curves) were obtained from vesicles in solutions of sodium salts with monovalent anions over a wide concentration range. These curves should be insensitive to any conformational effects due to ion binding. Indication of a conformational change in the lipid head group at low ion binding was obtained by studying the ratio between the contact and the pseudo-contact contributions. Besides the adsorption of lanthanide ions, specific anion binding to the surface was introduced to account for the enhanced chemical shifts (Cl- < Br- < NO3-). The results were analyzed in terms of the theory for the diffuse double layer (Gouy-Chapman-Grahame) with equilibrium conditions for the adsorbing cations and anions. Simulations of the titration curves furnished parameters for the ion-lipid interactions. The synergism between the cations and anions follows from the potential effects. Comparison of results with lanthanide ions and Ca2+ indicates that the anion adsorption probably depends on the nature of the adsorbed cation. Lanthanide ion binding to L-glycerophosphorylcholine is not influenced by sodium salts. The binding constant for this complex is weaker than with phosphatidylcholine. The chemical shifts for the lanthanide ion complexes with these two phosphorus compounds seem to be about the same.

Conformational states of the cell-penetrating peptide penetratin when interacting with phospholipid vesicles: effects of surface charge and peptide concentration.

The most commonly studied of the cell-penetrating peptides (CPP) is "penetratin" (pAntp), which functions as a carrier (vector), even for large hydrophilic (cargo) molecules. pAntp originates from the third helix of the Antennapedia homeodomain protein. The peptide is known to interact with negatively charged phospholipid vesicles, which leads to induction of secondary structure. In the present study, circular dichroism (CD) spectroscopy has been used to characterize the different secondary structures induced upon interaction with small unilamellar vesicles (SUVs) from mixtures of zwitterionic 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and negatively charged 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG). The interaction was monitored using an electron paramagnetic resonance (EPR) spin probe attached to the peptide, and the intrinsic fluorophore (tryptophan). We measured the secondary structure as a function of surface charge density, total lipid-to-peptide (L/P) molar ratio, and salt concentration, for completely bound peptide. With vesicles from POPG/POPC in a molar ratio below 30:70, at a high L/P, the peptide adopts a mainly helical conformation. Increasing the charge density, at the same L/P, promotes a higher degree of beta-structure. At a fixed charge density, reducing the L/P also results in an alpha-->beta structure conversion. Hence, low membrane surface charge density and low pAntp concentration both favor a mainly helical conformation, while high charge density and pAntp concentration promote a dominating beta-structure. We conclude that pAntp, when residing at the surface of a membrane, is chameleon-like in terms of its induced structure.

Molecular motion and order in oriented lipid multibilayer membranes evaluated by simulations of spin label ESR spectra. Effects of temperature, cholesterol and magnetic field.

A simulation method to interpret electron spin resonance (ESR) of spin labelled amphiphilic molecules in oriented phosphatidylcholine multibilayers in terms of a restricted motional model is presented. Order and motion of the cholestane spin label (3-spiro-doxyl-5alpha-cholestane) incorporated into egg yolk phosphatidylcholine, dipalmitoylphosphatidylcholine and dimyristoylphosphatidylcholine, pure and in mixture with cholesterol, were studied at various temperatures. With egg yolk phosphatidylcholine identical sets of motional parameters were obtained from simulations of ESR spectra obtained at three microwave frequencies (X-, K- and Q-band). With dipalmitoylphosphatidylcholine and dimyristoylphosphatidylcholine analyses of the spectra show that phase transitions occur in samples containing up to 30 mol % cholesterol. The activation energy for the motion of the spin label is about three times larger above than below the phase transition, indicating a more collective motion in the lipid crystalline state than in the gel state. In the liquid crystalline state the activation energy is larger in the pure phosphatidylcholines than with cholesterol added. Additions of cholesterol to egg phosphatidylcholine induces a higher molecular order but does not appreciably affect correlation times. This is in contrast to dipalmitoylphosphatidylcholine where both order and correlation times are affected by the presence of cholesterol. The activation energies follow the same order as the transition temperatures: dipalmitoylphosphatidylcholine greater than dimyristoylphosphatidylcholine greater than egg yokd phosphatidylcholine, suggesting a similar order of the cooperativity of the motion of the lipid molecules. Magnetic field-induced effects on egg phosphatidylcholine multibilayers were found at Q-band measurements above 40 degrees C. The cholestane spin label mimics order and motion of cholesterol molecule incorporated into the lipid bilayers. This reflects order and motion of the portions of the lipid molecules on the same depth of the bilayer as the rigid steroid portions of the intercalated molecules.

Cation requirement for the reconstitution of oligomycin-sensitive ATPase by means of soluble F1-ATPase and F1-depleted submitochondrial particles.

Bovine heart submitochondrial particles depleted of F1 by treatment with urea ("F1-depleted particles') were incubated with soluble F1-ATPase. The binding of F1 to the particles and the concomitant conferral of oligomycin sensitivity on the ATPase activity required the presence of cations in the incubation medium. NH4+, K+, Rb+, Na+ and Li+ promoted reconstitution maximally at 40-74 mM, guanidinium+ and Tris+ at 20-30 mM, and Ca2+ and Mg2+ at 3-5 mM. The particles exhibited a negative zeta-potential, as determined by microelectrophoresis, and this was neutralized by mono- and divalent cations in the same concentration range as that needed to promote F1 binding and reconstitution of oligomycin-sensitive ATPase. It is concluded that the cations act by neutralizing negative charges on the membrane surface, mainly negatively charged phospholipids. These results are discussed in relation to earlier findings reported in the literature with F1-depleted thylakoid membranes and with submitochondrial particles depleted of both F1 and the coupling proteins F6 and oligomycin sensitivity-conferring protein.

Surface potential effects on metal ion binding to phosphatidylcholine membranes 31P NMR study of lanthanide and calcium ion binding to egg-yolk lecithin vesicles.

31P NMR of phosphatidylcholine (lecithin) from egg-yolk in sonicated vesicles has been measured in the presence of various ions. Addition of Ln3+ or Ca2+ shifted the 31P resonance of the phosphate groups of the outer surface of the vesicles. These shifts were measured at varied lanthanide or Ca2+ concentration at different ionic strengths obtained by addition of NaCl. The shifts induced by Tb3+ and Ca2+ have been analyzed using the theory of the diffuse double layer. Corrections were introduced for the effect of the ionic strength on the activities of the ions. The binding efficiency is shown to be controlled by the electrostatic potential produced by the bound cations at the membrane surface. This potential is slightly modified due to weak chloride binding. Binding constants have been derived.

Interaction and structure induction of cell-penetrating peptides in the presence of phospholipid vesicles.

Certain short peptides, which are able to translocate across cell membranes with a low lytic activity, can be useful as carriers (vectors) for hydrophilic molecules. We have studied three such cell penetrating peptides: pAntp ('penetratin'), pIsl and transportan. pAntp and pIsl originate from the third helix of homeodomain proteins (Antennapedia and Isl-1, respectively). Transportan is a synthetic chimera (galanin and mastoparan). The peptides in the presence of various phospholipid vesicles (neutral and charged) and SDS micelles have been characterized by spectroscopic methods (fluorescence, EPR and CD). The dynamics of pAntp were monitored using an N-terminal spin label. In aqueous solution, the CD spectra of the three peptides show secondary structures dominated by random coil. With phospholipid vesicles, neutral as well as negatively charged, transportan gives up to 60% alpha-helix. pAntp and pIsl bind significantly only to negatively charged vesicles with an induction of around 60% beta-sheet-like secondary structure. With all three peptides, SDS micelles stabilize a high degree of alpha-helical structure. We conclude that the exact nature of any secondary structure induced by the membrane model systems is not directly correlated with the common transport property of these translocating peptides.

ESR spectral analysis of the molecular motion of spin labels in lipid bilayers and membranes based on a model in terms of two angular motional parameters and rotational correlation times.

Electron spin resonance (ESR) spectral line shapes are calculated for a nitroxide spin-labeled molecule undergoing rapid restricted rotations (twisting) about its long molecular axis while simultaneously tumbling within a cone. Explicit expressions are derived for the hyperfine splittings and g-values, as well as for the secular contributions to the motionally modulated linewidths. The present model is useful for analyzing the restricted twisting and tumbling motions, and rotational correlation times, of spin-labeled molecules in bilayers. Simulated spectra compare well with experimental spectra of lecithin bilayers marked with cholestane spin label, over a wide temperature range.

A left-handed 3(1) helical conformation in the Alzheimer Abeta(12-28) peptide.

We show for the first time that the secondary structure of the Alzheimer beta-peptide is in a temperature-dependent equilibrium between an extended left-handed 3(1) helix and a flexible random coil conformation. Circular dichroism spectra, recorded at 0.03 mM peptide concentration, show that the equilibrium is shifted towards increasing left-handed 3(1) helix structure towards lower temperatures. High resolution nuclear magnetic resonance (NMR) spectroscopy has been used to study the Alzheimer peptide fragment Abeta(12-28) in aqueous solution at 0 degrees C and higher temperatures. NMR translation diffusion measurements show that the observed peptide is in monomeric form. The chemical shift dispersion of the amide protons increases towards lower temperatures, in agreement with the increased population of a well-ordered secondary structure. The solvent exchange rates of the amide protons at 0 degrees C and pH 4.5 vary within at least two orders of magnitude. The lowest exchange rates (0.03-0.04 min(-1)) imply that the corresponding amide protons may be involved in hydrogen bonding with neighboring side chains.

Convective heat transfer on an inlet guide vane.

The flow and temperature fields around an inlet guide vane are determined numerically by a CFD method. Outer surface temperatures, heat transfer coefficient distributions, and static pressure distributions are presented. Three different thermal boundary conditions on the vane are analysed. The computed results are compared with experimental data. The governing equations are solved by a finite-volume method with the low Reynolds number version of the k-omega turbulence model by Wilcox implemented. It is found that the calculated results agree best with measurements if a conjugate heat transfer approach is applied and thus this wall condition is recommended for future investigations of film cooling of guide vanes and turbine blades.

Interaction of charged amphiphilic drugs with phosphatidylcholine vesicles studied by NMR.

Small unilamellar vesicles from egg phosphatidylcholine in NaCl solutions were exposed to some amphiphilic pharmaca. The aromatic drugs (chlorpromazine, dibucaine, tetracaine, imipramine and propranolol) were in their cationic form of the amines. By 1H- (100 and 400 MHz) and 31P- (40.5 and 161.7 MHz) NMR the membrane signals were observed. In particular, the N-methyl choline proton signals were followed upon drug addition. The intrinsic chemical shift difference (0.02 ppm) between the inner (upfield) and outer choline signals was influenced by the drug concentration. Packing properties of the lipid head groups and ring current shift probably contributed. At very high drug concentration, the vesicles are destroyed. A transformation into a micellar state with a high sample viscosity took place in a narrow concentration range of drug. The anion effects of Cl- were studied from the 35Cl-NMR linewidth at 9.8 and 39.1 MHz. A continuous increase in the signal linewidth followed upon drug addition to the vesicles. Only chlorpromazine produced a broadening in the absence of vesicles (NaCl blank). The linewidth reflected a critical micelle concentration of this drug around 7 mM in 0.1 M NaCl. The 35Cl-NMR experiments demonstrated the existence of an anionic counterion effect. This phenomenon should be accounted for when quantitatively analysing drug-membrane interactions in electrostatic terms.