Reduction of Ketones with LiAlH4 Complexes of α,α,α\u27,α\u27-Tetraaryl-1,3-dioxolane-4,5-dimethanols (TADDOLs) A Combination of Enantioselective Reduction and Clathrate Formation with a Discussion of LAH Reagents Bearing C2-Symmetrical Ligands

A complex prepared from one equivalent each of LiAlH4, EtOH and a TADDOL (α,α,α\u27,α\u27-tetraaryl-1,3-dioxolane-4,5-dimethanol) reduces aryl alkyl ketones to sec. alcohols with enantiomer ratios (er) up to 96 : 4. The chiral LAH derivative is used in two-fold excess in THF solution and at dry ice temperatures. The ability of TADDOLs to form clathrates diastereoselectively can be exploited to increase the er of the initially formed alcohols by a simple modification of the work-up procedure and hence, products of very high en- antiopurity (er 99 : 1) can be isolated. When (7i,/i)-TADDOLs (from (ZiA)-tartrate) are applied in the reaction, the 1-aryl-alkanols formed preferentially have (S) configuration, as for the products obtained with the corresponding (P)-BINOL and (P)-BIPHENOL derivatives. A common mechanistic model is discussed

Determining cantilever stiffness from thermal noise

Lübbe J, Temmen M, Rahe P, Kühnle A, Reichling M. Determining cantilever stiffness from thermal noise. Beilstein Journal of Nanotechnology. 2013;4:227-233.We critically discuss the extraction of intrinsic cantilever properties, namely eigenfrequency f(n), quality factor Q(n) and specifically the stiffness k(n) of the nth cantilever oscillation mode from thermal noise by an analysis of the power spectral density of displacement fluctuations of the cantilever in contact with a thermal bath. The practical applicability of this approach is demonstrated for several cantilevers with eigenfrequencies ranging from 50 kHz to 2 MHz. As such an analysis requires a sophisticated spectral analysis, we introduce a new method to determine kn from a spectral analysis of the demodulated oscillation signal of the excited cantilever that can be performed in the frequency range of 10 Hz to 1 kHz regardless of the eigenfrequency of the cantilever. We demonstrate that the latter method is in particular useful for noncontact atomic force microscopy (NC-AFM) where the required simple instrumentation for spectral analysis is available in most experimental systems

Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy

Lübbe J, Temmen M, Rode S, Rahe P, Kühnle A, Reichling M. Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy. Beilstein Journal of Nanotechnology. 2013;4:32-44.The noise of the frequency-shift signal Delta f in noncontact atomic force microscopy (NC-AFM) consists of cantilever thermal noise, tip-surface-interaction noise and instrumental noise from the detection and signal processing systems. We investigate how the displacement-noise spectral density d(z) at the input of the frequency demodulator propagates to the frequency-shift-noise spectral density d(Delta f) at the demodulator output in dependence of cantilever properties and settings of the signal processing electronics in the limit of a negligible tip-surface interaction and a measurement under ultrahigh-vacuum conditions. For a quantification of the noise figures, we calibrate the cantilever displacement signal and determine the transfer function of the signal-processing electronics. From the transfer function and the measured dz, we predict d(Delta f) for specific filter settings, a given level of detection-system noise spectral density d(ds)(z) and the cantilever-thermal-noise spectral density d(th)(z). We find an excellent agreement between the calculated and measured values for d(Delta f). Furthermore, we demonstrate that thermal noise in d(Delta f), defining the ultimate limit in NC-AFM signal detection, can be kept low by a proper choice of the cantilever whereby its Q-factor should be given most attention. A system with a low-noise signal detection and a suitable cantilever, operated with appropriate filter and feedback-loop settings allows room temperature NC-AFM measurements at a low thermal-noise limit with a significant bandwidth

PAA-PAMPS Copolymers as an Efficient Tool to Control CaCO3 Scale Formation

Dietzsch M, Barz M, Schüler T, et al. PAA-PAMPS Copolymers as an Efficient Tool to Control CaCO3 Scale Formation. Langmuir. 2013;29(9):3080-3088.Scale formation, the deposition of certain minerals such as CaCO3, MgCO3, and CaSO4 center dot 2H(2)O in industrial facilities and household devices, leads to reduced efficiency or severe damage. Therefore, incrustation is a major problem in everyday life. In recent years, double hydrophilic block copolymers (DHBCs) have been the focus of interest in academia with regard to their antiscaling potential. In this work, we synthesized well-defined blocklike PAA-PAMPS copolymers consisting of acrylic acid (AA) and 2-acrylamido-2-methyl-propane sulfonate (AMPS) units in a one-step reaction by RAFT polymerization. The derived copolymers had dispersities of 1.3 and below. The copolymers have then been investigated in detail regarding their impact on the different stages of the crystallization process of CaCO3. Ca2+ complexation, the first step of a precipitation process, and polyelectrolyte stability in aqueous solution have been investigated by potentiometric measurements, isothermal titration calorimetry (ITC), and dynamic light scattering (DLS). A weak Ca2+ induced copolymer aggregation without concomitant precipitation was observed. Nudeation, early particle growth, and colloidal stability have been monitored in situ with DLS. The copolymers retard or even completely suppress nucleation, most probably by complexation of solution aggregates. In addition, they stabilize existing CaCO3 particles in the nanometer regime. In situ AFM was used as a tool to verify the coordination of the copolymer to the calcite (104) crystal surface and to estimate its potential as a growth inhibitor in a supersaturated CaCO3 environment. All investigated copolymers instantly stopped further crystal growth. The carboxylate richest copolymer as the most promising antiscaling candidate proved its enormous potential in scale inhibition as well in an industrial-filming test (Fresenius standard method)

Experimental therapy and detection of glioblastoma: investigation of nanoparticles, ABCG2 modulators and optical imaging of intracerebral xenografts

The treatment of malignant brain tumors, especially of high-grade gliomas, poses one of the major challenges in cancer therapy. Despite seminal advancements in imaging techniques for the early diagnosis of CNS neoplasms as well as amendments in surgery and radiooncology, the prognosis of patients with glioma is very poor. The administration of temozolomide adjuvant to irradiation after resection of the tumor - the current “gold standard” in the treatment of glioblastoma - has only marginally improved median survival by ca. 3 months. Hence, there is an urgent need for novel approaches to the treatment of malignant brain tumors. To investigate the efficiency of such regimens in vivo, predictive preclinical animal models are indispensible. In this thesis, three subject areas were dealt with: - evaluation of doxorubicin-loaded poly(butylcyanoacrylate) (PBCA) nanoparticle (NP) formulations as drug-carriers, - modulation of the ATP-binding cassette transporter ABCG2, which is expressed in brain capillaries, by newly synthesized inhibitors, as a strategy to overcome the blood-brain barrier (BBB) with chemotherapeutics, which are substrates of this efflux pump, and - refinement of orthotopic glioblastoma models in nude mice to allow noninvasive optical imaging of intracerebral tumors. Human glioblastoma cells U-87 MG, U-118 MG and U-373 MG were incubated with free doxorubicin and doxorubicin loaded onto PBCA NPs. As the glioblastoma cells do neither express ABCB1 nor ABCG2, Kb-V1 and MCF-7/Topo cells were included, to study effects on both efflux pumps. In the crystal-violet chemosensitivity assay, cytotoxicities of the doxorubicin-loaded NPs and of the dissolved cytostatic were similar against all glioblastoma cells. By contrast, a higher efficacy of the NP formulations was observed on ABCB1-overexpressing Kb-V1, but not on ABCG2-expressing MCF-7/Topo cells, indicating an interaction of the NPs with the ABCB1 efflux pump. Therefore, increased drug concentrations in the brain after administration of such drug-loaded NPs to animals, as reported in literature, might be due interactions of the NPs with ABCB1 at the BBB. The modulation of ABC transporters at the BBB represents an attractive strategy to increase intracerebral levels of drugs, which are known to be substrates of such efflux pumps. For this reason, the identification of potent efflux pump inhibitors is a promising approach to improve the chemotherapy of brain tumors. A series of analogs, derived from the original ABCB1 inhibitor tariquidar, was investigated for potency against ABCG2 and selectivity vs. ABCB1. To expand methodology and to by-pass problems associated with the flow cytometric (FACS) mitoxantrone-efflux assay, two 96-well plate assays, using the fluorescent ABCG2 substrates Hoechst 33342 and pheophorbide a, were developed. Interestingly, slight structural modifications of tariquidar analogs yielded potent and selective inhibitors of ABCG2. The most potent modulator showed an IC50 value of 60 nM in the FACS assay and 65 and 126 nM in the microtiter plate assays. In view of future in vivo studies, the most potent inhibitors were investigated for stability in plasma by the means of HPLC-MS analysis. Unfortunately, these compounds are prone to rapid enzymatic cleavage at the central benzamide moiety. Therefore, compounds with improved drug-like properties are required. Since a regulation of ABCG2 by estrogens is discussed in literature, MCF-7/Topo cells were treated with estradiol and subjected to treatment with topotecan. No differences in the antiproliferative effect between estradiol-treated and non-treated controls were observed, indicating, at best, a therapeutically irrelevant regulation of the ABCG2-level by estradiol. To investigate the therapeutic value of new concepts, e.g. the combined administration of selective inhibitors of ABC-transporters with appropriate cytostatics, the main focus of this work was the refinement of in vivo xenograft models. Indeed, orthotopic brain tumor models, allowing the monitoring of tumor progression by noninvasive optical imaging, were established in nude mice. For this purpose, human U-87 MG glioblastoma cells were transfected with the genes encoding luciferase2 (Luc2) and the recently discovered far-red fluorescent protein Katushka (Kat), respectively. Numerous clones were characterized in vitro with respect to bioluminescence / fluorescence, growth kinetics and chemosensitivity. As the transfectants were tumorigenic subcutaneously (s.c.), and Luc2 as well as Kat expression persisted in the s.c. model, the human glioblastoma variants were injected into the brains of nude mice, where reproducibly growing tumors developed. Most important is the fact that these intracerebral xenografts were accessible to both, bioluminescence and fluorescence imaging. Moreover, there was a direct correlation between the optical signals and the tumor load, confirmed by histology

Solid phase synthesis of tariquidar-related modulators of ABC transporters preferring breast cancer resistance protein (ABCG2)

Aiming at structural optimization of potent and selective ABCG2 inhibitors, such as UR-ME22-1, from our laboratory, an efficient solid phase synthesis was developed to get convenient access to this class of compounds. 7-Carboxyisatoic anhydride was attached to Wang resin to give resin bound 2-aminoterephthalic acid. Acylation with quinoline-2- or -6-carbonyl chlorides, coupling with tetrahydroisoquinolinylethylphenylamine derivatives, cleavage of the carboxylic acids from solid support and treatment with trimethylsilydiazomethane gave the corresponding methyl esters. Among these esters highly potent and selective ABCG2 modulators were identified (inhibition of ABCB1 and ABCG2 determined in the calcein-AM and the Hoechst 33342 microplate assay, respectively). Interestingly, compounds bearing triethyleneglycol ether groups at the tetrahydroisoquinoline moiety (UR-COP77, UR-COP78) were comparable to UR-ME22-1 in potency but considerably more efficient (max inhibition 83% and 88% vs 60%, rel. to fumitremorgin c, 100%) These results support the hypothesis that solubility of the new ABCG2 modulators and of the reference compounds tariquidar and elacridar in aqueous media is the efficacy-limiting factor

BK K+ channel blockade inhibits radiation-induced migration/brain infiltration of glioblastoma cells

Infiltration of the brain by glioblastoma cells reportedly requires Ca2+ signals and BK K+ channels that program and drive glioblastoma cell migration, respectively. Ionizing radiation (IR) has been shown to induce expression of the chemokine SDF-1, to alter the Ca2+ signaling, and to stimulate cell migration of glioblastoma cells. Here, we quantified fractionated IR-induced migration/brain infiltration of human glioblastoma cells in vitro and in an orthotopic mouse model and analyzed the role of SDF-1/CXCR4 signaling and BK channels. To this end, the radiation-induced migratory phenotypes of human T98G and far-red fluorescent U-87MG-Katushka glioblastoma cells were characterized by mRNA and protein expression, fura-2 Ca2+ imaging, BK patch-clamp recording and transfilter migration assay. In addition, U-87MG-Katushka cells were grown to solid glioblastomas in the right hemispheres of immunocompromised mice, fractionated irradiated (6 MV photons) with 5 x 0 or 5 x 2 Gy, and SDF-1, CXCR4, and BK protein expression by the tumor as well as glioblastoma brain infiltration was analyzed in dependence on BK channel targeting by systemic paxilline application concomitant to IR. As a result, IR stimulated SDF-1 signaling and induced migration of glioblastoma cells in vitro and in vivo. Importantly, paxilline blocked IR-induced migration in vivo. Collectively, our data demonstrate that fractionated IR of glioblastoma stimulates and BK K+ channel targeting mitigates migration and brain infiltration of glioblastoma cells in vivo. This suggests that BK channel targeting might represent a novel approach to overcome radiation-induced spreading of malignant brain tumors during radiotherapy

A Modeling Approach to the Self-Assembly of the Golgi Apparatus

The dynamic compartmentalization of eukaryotic cells is a fascinating phenomenon that is not yet understood. A prominent example of this challenge is the Golgi apparatus, the central hub for protein sorting and lipid metabolism in the secretory pathway. Despite major advances in elucidating its molecular biology, the fundamental question of how the morphogenesis of this organelle is organized on a system level has remained elusive. Here, we have formulated a coarse-grained computational model that captures key features of the dynamic morphogenesis of a Golgi apparatus. In particular, our model relates the experimentally observed Golgi phenotypes, the typical turnover times, and the size and number of cisternae to three basic, experimentally accessible quantities: the rates for material influx from the endoplasmic reticulum, and the anterograde and retrograde transport rates. Based on these results, we propose which molecular factors should be mutated to alter the organelle's phenotype and dynamics

Survival in primary hemophagocytic lymphohistiocytosis, 2016 to 2021: etoposide is better than its reputation

Böhm S, Wustrau K, Pachlopnik Schmid J, et al. Survival in primary hemophagocytic lymphohistiocytosis, 2016 to 2021: etoposide is better than its reputation. Blood. 2024;143(10):872-881.ABSTRACT: Primary hemophagocytic lymphohistiocytosis (pHLH) is a life-threatening hyperinflammatory syndrome that develops mainly in patients with genetic disorders of lymphocyte cytotoxicity and X-linked lymphoproliferative syndromes. Previous studies with etoposide-based treatment followed by hematopoetic stem cell transplantation (HSCT) resulted in 5-year survival of 50% to 59%. Contemporary data are lacking. We evaluated 88 patients with pHLH documented in the international HLH registry from 2016-2021. In 12 of 88 patients, diagnosis was made without HLH activity, based on siblings or albinism. Major HLH-directed drugs (etoposide, antithymocyte globulin, alemtuzumab, emapalumab, ruxolitinib) were administered to 66 of 76 patients who were symptomatic (86% first-line etoposide); 16 of 57 patients treated with etoposide and 3 of 9 with other first-line treatment received salvage therapy. HSCT was performed in 75 patients; 7 patients died before HSCT. Three-year probability of survival (pSU) was 82% (confidence interval [CI], 72%-88%) for the entire cohort and 77% (CI, 64%-86%) for patients receiving first-line etoposide. Compared with the HLH-2004 study, both pre-HSCT and post-HSCT survival of patients receiving first-line etoposide improved, 83% to 91% and 70% to 88%. Differences to HLH-2004 included preferential use of reduced-toxicity conditioning and reduced time from diagnosis to HSCT (from 148 to 88 days). Three-year pSU was lower with haploidentical (4 of 9 patients [44%]) than with other donors (62 of 66 [94%]; P< .001). Importantly, early HSCT for patients who were asymptomatic resulted in 100% survival, emphasizing the potential benefit of newborn screening. This contemporary standard-of-care study of patients with pHLH reveals that first-line etoposide-based therapy is better than previously reported, providing a benchmark for novel treatment regimes. © 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies