BioRef: The Reflectometer for Biological Applications (V18) at BER II

The time-of-flight neutron reflectometer BioRef is dedicated to the investigation of solid-liquid interfaces, in particular for soft matter applications. The possibility to mount a FTIR-ATR to the sample stage offers the possibility of combined in-situ measurements

La dynamique des systèmes biologiques en fonction de l’hydratation, de la température et de la pression étudiée pardiffusion neutronique

Incoherent elastic and quasi-elastic neutron scattering were used to measure membrane and protein dynamics in the nano- to picosecond time and Ångstrom length scale.The hydration dependent dynamics of DMPC model membranes was studied using elastic and quasi-elastic neutron scattering. The elastic experiments showed a clear shift of the temperature of the main phase transition to higher temperatures with decreasing hydration level.The performed quasi-elastic measurements demonstrated nicely the influence, hydration has on the diffusive motions of the head lipid groups. Different models are necessary to fit the Q-dependence of the elastic incoherent structure factor and show therefore the reduced mobility as a result of reduced water content.In addition to temperature, pressure as a second thermodynamical variable was used to explore dynamics of DMPC membranes. The ordering introduced by applying pressure has similar effect to decreased hydration, therefore both approaches are complementary. Covering three orders of magnitude in observation time, the dynamics of native AChE and its complexed counterpart in presence of Huperzin A was investigated in the range from 1 ns to 100 ps. The mean square displacements obtained from the elastic data allowed the determination of activation energies and gave evidence that a hierarchyof motions contributes to the enzymatic activity. Diffusion constants and residence times were extracted from the quasi-elastic broadening.La diffusion incohérente élastique et quasi-élastique de neutrons a été utilisée pour mesurer la dynamique de membranes et de protéines à l’échelle de la pico- à la nanoseconde et de la longueur de l’Ångstrom.La dynamique de membranes modèles DMPC, en fonction de l’hydratation a été étudiée par diffusion neutronique. Les expériences élastiques ont, clairement montré un décalage de la température de transition de phase principale vers une température plus haute pour une diminution du niveau d’hydratation.Les mesures quasi-élastiques effectuées ont montré l’influence de l’hydratation sur les mouvements diffusifs des têtes lipidiques. Différents modèles ont été nécessaires pour affiner les dépendances en Q des facteurs de structure élastiques incohérents et montrent donc la mobilité réduite due à l’hydratation inférieure.En plus de la température, la pression comme deuxième variable thermodynamique a été utilisée pour étudier la dynamique des membranes DMPC. L’ordre induit par l’application d’une pression a un effet similaire à une hydratation diminuée, donc les deux approches sont complémentaires.Couvrant trois ordres de grandeur, la dynamique d’AChE libre ou complexée avec de l’Huperzine A a été étudiée dans le domaine allant de 1 ns à 100 ps. Les déplacements carrés moyens obtenues à partir des données élastiques ont permis la détermination des énergies d’activation et prouvent que toute une hiérarchie de mouvements contribue a l’activité enzymatique. Les constantes de diffusion et les temps de corrélation ont été extraits de l’élargissement quasi-élastique

La dynamique des systèmes biologiques en fonction de l’hydratation, de la température et de la pression étudiée pardiffusion neutronique

Incoherent elastic and quasi-elastic neutron scattering were used to measure membrane and protein dynamics in the nano- to picosecond time and Ångstrom length scale.The hydration dependent dynamics of DMPC model membranes was studied using elastic and quasi-elastic neutron scattering. The elastic experiments showed a clear shift of the temperature of the main phase transition to higher temperatures with decreasing hydration level.The performed quasi-elastic measurements demonstrated nicely the influence, hydration has on the diffusive motions of the head lipid groups. Different models are necessary to fit the Q-dependence of the elastic incoherent structure factor and show therefore the reduced mobility as a result of reduced water content.In addition to temperature, pressure as a second thermodynamical variable was used to explore dynamics of DMPC membranes. The ordering introduced by applying pressure has similar effect to decreased hydration, therefore both approaches are complementary. Covering three orders of magnitude in observation time, the dynamics of native AChE and its complexed counterpart in presence of Huperzin A was investigated in the range from 1 ns to 100 ps. The mean square displacements obtained from the elastic data allowed the determination of activation energies and gave evidence that a hierarchyof motions contributes to the enzymatic activity. Diffusion constants and residence times were extracted from the quasi-elastic broadening.La diffusion incohérente élastique et quasi-élastique de neutrons a été utilisée pour mesurer la dynamique de membranes et de protéines à l’échelle de la pico- à la nanoseconde et de la longueur de l’Ångstrom.La dynamique de membranes modèles DMPC, en fonction de l’hydratation a été étudiée par diffusion neutronique. Les expériences élastiques ont, clairement montré un décalage de la température de transition de phase principale vers une température plus haute pour une diminution du niveau d’hydratation.Les mesures quasi-élastiques effectuées ont montré l’influence de l’hydratation sur les mouvements diffusifs des têtes lipidiques. Différents modèles ont été nécessaires pour affiner les dépendances en Q des facteurs de structure élastiques incohérents et montrent donc la mobilité réduite due à l’hydratation inférieure.En plus de la température, la pression comme deuxième variable thermodynamique a été utilisée pour étudier la dynamique des membranes DMPC. L’ordre induit par l’application d’une pression a un effet similaire à une hydratation diminuée, donc les deux approches sont complémentaires.Couvrant trois ordres de grandeur, la dynamique d’AChE libre ou complexée avec de l’Huperzine A a été étudiée dans le domaine allant de 1 ns à 100 ps. Les déplacements carrés moyens obtenues à partir des données élastiques ont permis la détermination des énergies d’activation et prouvent que toute une hiérarchie de mouvements contribue a l’activité enzymatique. Les constantes de diffusion et les temps de corrélation ont été extraits de l’élargissement quasi-élastique

Polymer-induced swelling of solid-supported lipid membranes

In this paper, we study the interaction of charged polymers with solid-supported 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes by in-situ neutron reflectivity. We observe an enormous swelling of the oligolamellar lipid bilayer stacks after incubation in solutions of poly(allylamine hydrochloride) (PAH) in DO. The positively charged polyelectrolyte molecules interact with the lipid bilayers and induce a drastic increase in their d-spacing by a factor of ~4. Temperature, time, and pH influence the swollen interfacial lipid linings. From our study, we conclude that electrostatic interactions introduced by the adsorbed PAH are the main cause for the drastic swelling of the lipid coatings. The DMPC membrane stacks do not detach from their solid support at T > T. Steric interactions, also introduced by the PAH molecules, are held responsible for the stabilizing effect. We believe that this novel system offers great potential for fundamental studies of biomembrane properties, keeping the membrane's natural fluidity and freedom, decoupled from a solid support at physiological conditions

Outcome after PSMA-PET/CT-based salvage radiotherapy for nodal recurrence after radical prostatectomy

PURPOSE Nodal recurrent prostate cancer (PCa) represents a common state of disease, amenable to local therapy. PSMA-PET/CT detects PCa recurrence at low PSA levels. The aim of this study was to evaluate the outcome of PSMA-PET/CT-based salvage radiotherapy (sRT) for lymph node (LN) recurrence. METHODS A total of 100 consecutive patients treated with PSMA-PET/CT-based salvage elective nodal radiotherapy (sENRT) for LN recurrence were retrospectively examined. Patients underwent PSMA-PET/CT scan due to biochemical persistence (bcP, 76%) or biochemical recurrence (bcR, 24%) after radical prostatectomy (RP). Biochemical recurrence-free survival (BRFS) defined as PSA 1~ng/ml) with improved DMFS, respectively. No such association was seen for the number of affected lymph nodes. CONCLUSIONS Overall, the present analysis shows that the so far, unmatched sensitivity and specificity of PSMA-PET/CT translates in comparably high BRFS and DMFS after PSMA-PET/CT-based sENRT for patients with PCa LN recurrence. Concomitant ADT, duration of ADT, PSA value before sRT, and localization of LN metastases were significant factors for improved outcome

The maximum standardized uptake value in patients with recurrent or persistent prostate cancer after radical prostatectomy and PSMA-PET-guided salvage radiotherapy-a multicenter retrospective analysis

Purpose This study aims to evaluate the association of the maximum standardized uptake value (SUVmax) in positron-emission tomography targeting prostate-specific membrane antigen (PSMA-PET) prior to salvage radiotherapy (sRT) on biochemical recurrence free survival (BRFS) in a large multicenter cohort.Methods Patients who underwent (68) Ga-PSMA11-PET prior to sRT were enrolled in four high-volume centers in this retrospective multicenter study. Only patients with PET-positive local recurrence (LR) and/or nodal recurrence (NR) within the pelvis were included. Patients were treated with intensity-modulated-sRT to the prostatic fossa and elective lymphatics in case of nodal disease. Dose escalation was delivered to PET-positive LR and NR. Androgen deprivation therapy was administered at the discretion of the treating physician. LR and NR were manually delineated and SUVmax was extracted for LR and NR. Cox-regression was performed to analyze the impact of clinical parameters and the SUVmax-derived values on BRFS.Results Two hundred thirty-five patients with a median follow-up (FU) of 24 months were included in the final cohort. Two-year and 4-year BRFS for all patients were 68% and 56%. The presence of LR was associated with favorable BRFS (p = 0.016). Presence of NR was associated with unfavorable BRFS (p = 0.007). While there was a trend for SUVmax values >= median (p = 0.071), SUVmax values >= 75% quartile in LR were significantly associated with unfavorable BRFS (p = 0.022, HR: 2.1, 95%CI 1.1-4.6). SUVmax value in NR was not significantly associated with BRFS. SUVmax in LR stayed significant in multivariate analysis (p = 0.030). Sensitivity analysis with patients for who had a FU of > 12 months (n = 197) confirmed these results.Conclusion The non-invasive biomarker SUVmax can prognosticate outcome in patients undergoing sRT and recurrence confined to the prostatic fossa in PSMA-PET. Its addition might contribute to improve risk stratification of patients with recurrent PCa and to guide personalized treatment decisions in terms of treatment intensification or de-intensification. This article is part of the Topical Collection on Oncology-Genitourinary

Circulating Endothelial Progenitor Cells in Kidney Transplant Patients

Background: Kidney transplantation (RTx) leads to amelioration of endothelial function in patients with advanced renal failure. Endothelial progenitor cells (EPCs) may play a key role in this repair process. The aim of this study was to determine the impact of RTx and immunosuppressive therapy on the number of circulating EPCs. Methods: We analyzed 52 RTx patients (58613 years; 33 males, mean 6 SD) and 16 age- and gender-matched subjects with normal kidney function (57617; 10 males). RTx patients received a calcineurin inhibitor (CNI)-based (65%) or a CNI-free therapy (35%) and steroids. EPC number was determined by double positive staining for CD133/VEGFR2 and CD34/VEGFR2 by flow cytometry. Stromal cell-derived factor 1 alpha (SDF-1) levels were assessed by ELISA. Experimentally, to dissociate the impact of RTx from the impact of immunosuppressants, we used the 5/6 nephrectomy model. The animals were treated with a CNI-based or a CNI-free therapy, and EPCs (Sca+cKit+) and CD26+ cells were determined by flow cytometry. Results: Compared to controls, circulating number of CD34+/VEGFR2+ and CD133+/VEGFR2+ EPCs increased in RTx patients. There were no correlations between EPC levels and statin, erythropoietin or use of renin angiotensin system blockers in our study. Indeed, multivariate analysis showed that SDF-1 – a cytokine responsible for EPC mobilization – is independently associated with the EPC number. 5/6 rats presented decreased EPC counts in comparison to control animals. Immunosuppressive therapy was able to restore normal EPC values in 5/6 rats. These effects on EPC number were associated with reduced number of CD26+ cells, which might be related to consequent accumulation of SDF-1. Conclusions: We conclude that kidney transplantation and its associated use of immunosuppressive drugs increases the number of circulating EPCs via the manipulation of the CD26/SDF-1 axis. Increased EPC count may be associated to endothelial repair and function in these patients.