Atmospheric pollution, soil nutrients and climate effects on Mucoromycota arbuscular mycorrhizal fungi.

Fine root endophyte mycorrhizal fungi in the Endogonales (Mucoromycota arbuscular mycorrhizal fungi, M-AMF) are now recognized as at least as important globally as Glomeromycota AMF (G-AMF), yet little is known about the environmental factors which influence M-AMF diversity and colonization, partly because they typically only co-colonize plants with G-AMF. Wild populations of Lycopodiella inundata predominantly form mycorrhizas with M-AMF and therefore allow focussed study of M-AMF environmental drivers. Using microscopic examination and DNA sequencing we measured M-AMF colonization and diversity over three consecutive seasons and modelled interactions between these response variables and environmental data. Significant relationships were found between M-AMF colonization and soil S, P, C:N ratio, electrical conductivity, and the previously overlooked micronutrient Mn. Estimated N deposition was negatively related to M-AMF colonization. Thirty-nine Endogonales Operational Taxonomic Units (OTUs) were identified in L. inundata roots, a greater diversity than previously recognized in this plant. Endogonales OTU richness correlated negatively with soil C:N while community composition was mostly influenced by soil P. This study provides first evidence that M-AMF have distinct ecological preferences in response to edaphic variables also related to air pollution. Future studies require site-level atmospheric pollution monitoring to guide critical load policy for mycorrhizal fungi in heathlands and grasslands.

Inhibition of colony stimulating factor-1 receptor abrogates microenvironment-mediated therapeutic resistance in gliomas.

Glioblastomas represent the most aggressive glioma grade and are associated with a poor patient prognosis. The current standard of care, consisting of surgery, radiation and chemotherapy, only results in a median survival of 14 months, underscoring the importance of developing effective new therapeutic strategies. Among the challenges in treating glioblastomas are primary resistance and the rapid emergence of recurrent disease, which can result from tumor cell-intrinsic mechanisms in addition to tumor microenvironment (TME)-mediated extrinsic resistance. Using a PDGF-B-driven proneural glioma mouse model, we assessed a panel of tyrosine kinase inhibitors with different selectivity profiles. We found that PLX3397, an inhibitor of colony stimulating factor-1 receptor (CSF-1R), blocks glioma progression, markedly suppresses tumor cell proliferation and reduces tumor grade. By contrast, the multi-targeted tyrosine kinase inhibitors dovitinib and vatalanib, which directly target tumor cells, exert minimal anti-tumoral effects in vivo, despite killing glioma cells in vitro, suggesting a TME-mediated resistance mechanism may be involved. Interestingly, PLX3397 interferes with tumor-mediated education of macrophages and consequently restores the sensitivity of glioma cells to tyrosine kinase inhibitors in vivo in preclinical combination trials. Our findings thus demonstrate that microenvironmental alteration by CSF-1R blockade renders tumor cells more susceptible to receptor tyrosine kinase inhibition in a preclinical glioblastoma model, which may have important translational relevance.

Association between high on-treatment platelet reactivity and occurrence of cerebral ischemic events in patients undergoing percutaneous coronary intervention.

INTRODUCTION: Percutaneous coronary angioplasty (PCI) has become a routine treatment in symptomatic patients with coronary artery disease. The use of new generation drug eluting stents (DES) and dual antiplatelet therapy has significantly improved treatment outcomes and increased patients' safety by reducing the risk of stent thrombosis. AIMS: The goal of this study was to assess whether high on treatment platelet reactivity (HTPR), despite clopidogrel treatment, measured with Multiplate Electrode Aggregometer (MEA) is associated with the risk of adverse ischemic cerebral events. METHODS: Symptomatic patients with coronary artery disease admitted for coronary angiography and angioplasty (PCI) were consecutively enrolled in this study. 249 consecutive patients underwent coronary artery stenting for stable angina (n=215) or non-ST-elevation acute coronary syndrome (n=34). Inhibition of platelet aggregation was assessed by MEA. Genetic polymorphism of CYP2C19 was tested by HRM Real-Time PCR method in 150 patients. RESULTS: Patients with HTPR were more frequently diagnosed with ischemic stroke (p=0.0351, OR=16.818, 95% CI [1.464-193.23]) and other ischemic cerebral events (stroke or TIA, p=0.0339, OR=6.5, 95% CI [1.36-31.07]). Cumulative assessment of all ischemic and hemorrhagic events showed no statistical significance. Cerebral ischemic event was the only adverse event that correlated with CYP2C19 (*2/*2) allele (p=0.0489, OR=10; 95% CI [1.39-71.80]). CONCLUSIONS: HTPR assessed by MEA, in patients treated with clopidogrel after coronary artery stenting was found to be an important risk factor of ischemic cerebral events. In concordance, the carriers of CYP2C19*2/*2 allele showed an increased rate of ischemic cerebral events.

Insight into species diversity of the Trichostrongylidae Leiper, 1912 (Nematoda: Strongylida) in ruminants.

This paper focuses on the species diversity among the Trichostrongylidae Leiper, 1912 (Nematoda: Strongylida), and complexity of the family systematics. Polymorphism (subfamilies: Ostertagiinae, Cooperiinae and Haemonchinae), the presence of cryptic species (genus: Teladorsagia) and hybridization (genera: Cooperia, Haemonchus and Ostertagia) are presented and discussed, considering both morphological and molecular evidence. Some of these phenomena are common, nevertheless not sufficiently understood, which indicates the need for expanding the current state of knowledge thereof. Within the Trichostrongylidae, species distinction supported merely by morphological features is difficult, and requires confirmation by means of molecular methods. The parasitic nematode taxonomy is complicated mainly by the genus Teladorsagia, but complexity may also be expected among other Ostertagiinae (e.g. in the genera Ostertagia and Marshallagia). The data presented here show that the members of the Trichostrongylidae can significantly complicate unambiguous species identification. Hence, it is essential to consider the phenomena mentioned, to gather valid and comparable data on the biodiversity of this family.

ATP release, generation and hydrolysis in exocrine pancreatic duct cells.

Extracellular adenosine triphosphate (ATP) regulates pancreatic duct function via P2Y and P2X receptors. It is well known that ATP is released from upstream pancreatic acinar cells. The ATP homeostasis in pancreatic ducts, which secrete bicarbonate-rich fluid, has not yet been examined. First, our aim was to reveal whether pancreatic duct cells release ATP locally and whether they enzymatically modify extracellular nucleotides/sides. Second, we wished to explore which physiological and pathophysiological factors may be important in these processes. Using a human pancreatic duct cell line, Capan-1, and online luminescence measurement, we detected fast ATP release in response to pH changes, bile acid, mechanical stress and hypo-osmotic stress. ATP release following hypo-osmotic stress was sensitive to drugs affecting exocytosis, pannexin-1, connexins, maxi-anion channels and transient receptor potential cation channel subfamily V member 4 (TRPV4) channels, and corresponding transcripts were expressed in duct cells. Direct stimulation of intracellular Ca(2+) and cAMP signalling and ethanol application had negligible effects on ATP release. The released ATP was sequentially dephosphorylated through ecto-nucleoside triphosphate diphosphohydrolase (NTPDase2) and ecto-5'-nucleotidase/CD73 reactions, with respective generation of adenosine diphosphate (ADP) and adenosine and their maintenance in the extracellular medium at basal levels. In addition, Capan-1 cells express counteracting adenylate kinase (AK1) and nucleoside diphosphate kinase (NDPK) enzymes (NME1, 2), which contribute to metabolism and regeneration of extracellular ATP and other nucleotides (ADP, uridine diphosphate (UDP) and uridine triphosphate (UTP)). In conclusion, we illustrate a complex regulation of extracellular purine homeostasis in a pancreatic duct cell model involving: ATP release by several mechanisms and subsequent nucleotide breakdown and ATP regeneration via counteracting nucleotide-inactivating and nucleotide-phosphorylating ecto-enzymes. We suggest that extracellular ATP homeostasis in pancreatic ducts may be important in pancreas physiology and potentially in pancreas pathophysiology.

Development and evaluation of short forms of the Pain Catastrophizing Scale and the Pain Self-efficacy Questionnaire.

BACKGROUND: To facilitate efficient screening and reduce the length of comprehensive self-report batteries, a four-item short form of the Pain Catastrophizing Scale (PCS) and a two-item short form of the Pain Self-Efficacy Questionnaire (PSEQ) have been developed and evaluated in samples of patients with arm and upper extremity pain. AIMS: The first aim of this study was to evaluate these short forms in a heterogeneous sample of patients seeking treatment for chronic musculoskeletal pain, using a priori criteria for determining adequate internal consistency, construct validity and sensitivity to change. In addition, the findings of past studies were used to identify items suitable for new and potentially stronger short forms of these measures. METHOD: Data were provided by 280 patients who completed the original PCS and PSEQ as part of an interdisciplinary rehabilitation programme. RESULTS: The previously developed four-item PCS and the newly developed six-item short form of the PCS both met the internal consistency and construct validity criteria. They did not meet the criterion regarding sensitivity to change. However, similar to what was obtained using the original PCS, large effect sizes were found when using these short forms to examine pre-treatment to post-treatment changes in catastrophizing. For the PSEQ, the new four-item short form was clearly superior to the other alternatives and met all three criteria. CONCLUSION: The strongest short forms of the PCS and PSEQ could facilitate the assessment of pain catastrophizing and self-efficacy in situations in which the use of the longer original measures is not feasible.

Comparison of the antiplatelet effect of two clopidogrel bisulfate formulations: Plavix and generic-Egitromb.

Due to expansion of the pharmaceutical market it seems necessary to prove the efficacy of the generic drugs. The aim of this study is to compare the effects of two clopidogrel formulations: brand-name-Plavix and generic drug - Egitromb. This is a prospective, randomized study comparing two groups of patients treated with two clopidogrel: brand-name Plavix and generic drug- Egitromb. The 53 consecutive patients with stable coronary artery disease qualifying for coronary angiography and PCI were enrolled in this trial. They were randomized into two groups. In the group A (n = 28) patients received Egitromb 300 mg at admission followed by 8 days of 75 mg Egitromb daily. In the group B (n = 25) patients received Plavix 300 mg on the admission followed by 8 days of 75 mg Plavix maintenance therapy. Blood samples for multiple electrode aggregometry testing were drawn at baseline, 5 hours and 8 days after taking the loading dose. Median values of platelet aggregation inhibition did not differ between the Plavix and Egitromb groups when assessed at baseline: 239AU/min (IQR:329) vs. 209 (IQR:406; p = 0.894), 5 hours after loading: 183 AU/min (IQR:107) vs. 165 (IQR:171; p = 0.831) or at day 8: 174 AU/min (IQR:133) vs. 211 (IQR:133; p = 0.332. The study showed no difference in the therapeutic effect of two clopidogrel formulations (Egitromb and Plavix).

Prognostic usefulness of IL-6 and VEGF for the occurrence of changes in coronary arteries of patients with stable angina and implanted stents.

AIM: The aim of this study was to determine the prognostic significance of interleukin 6 (IL-6) and vascular endothelial growth factor (VEGF) in patients with chronic coronary artery disease treated who underwent percutaneous coronary intervention with stent implantation, for assessing the risk of restenosis and the occurrence of de novo lesions. PATIENTS AND METHODS: 498 patients with stable angina were examined during 18 months. 50 patients with significant (> 70%) stenosis of one coronary artery, eligible for the implantation of one stent, were enrolled to the study. Il-6 and VEGF level was measured using ELISA immunoassays during the initial coronary angiography with simultaneous angioplasty and stent implantation and 4 weeks after stent implantation. Coronary angiography was carried out 8-12 months after stent implantation. RESULTS: Statistically significant increase in IL-6 (from 4.02 ± 4.40 to 10.90 ± 8.23) and VEGF (from 310.13 ± 50.90 to 392.32 ± 106.84) level was observed 4 weeks after stent implantation in the group with restenosis. CONCLUSIONS: Increased levels of IL-6 and VEGF in the peripheral blood of patients with chronic stable angina pectoris, measured 4 weeks after coronary angioplasty with stent implantation, may indicate an increased risk of angiographic restenosis and de novo coronary artery lesions.

Role of vesicular nucleotide transporter VNUT (SLC17A9) in release of ATP from AR42J cells and mouse pancreatic acinar cells.

ATP is released from cells in response to various stimuli. Our previous studies on pancreas indicated that pancreatic acini could be major stores of secreted ATP. In the present study, our aim was to establish the role of the vesicular nucleotide transporter (VNUT), SLC17A9, in storage and release of ATP. Freshly prepared acini from mice and AR42J rat acinar cells were used in this study. We illustrate that in AR42J cells, quinacrine (an ATP store marker) and Bodipy ATP (a fluorescent ATP analog) co-localized with VNUT-mCherry to vesicles/granules. Furthermore, in acini and AR42J cells, a marker of the zymogen granule membranes, Rab3D, and VNUT co-localized. Dexamethasone treatment of AR42J cells promoted formation of acinar structures, paralleled by increased amylase and VNUT expression, and increased ATP release in response to cholinergic stimulation. Mechanical stimulus (pressure) and cell swelling also induced ATP release, but this was not influenced by dexamethasone, most likely indicating different non-zymogen-related release mechanism. In conclusion, we propose that VNUT-dependent ATP release pathway is associated with agonist-induced secretion process and downstream purinergic signalling in pancreatic ducts.

Left ventricular diastolic dysfunction is associated with impaired baroreflex at rest and during orthostatic stress in hypertensive patients with left ventricular hypertrophy.

The study aimed to determine the relationship between left ventricular (LV) diastolic function and the heart's spontaneous baroreflex at rest and in response to orthostatic stress during a prospective follow-up of hypertensive patients with LV hypertrophy (LVH+). LV structure and function and baroreflex sensitivity (BRS) during tilt testing were evaluated in 24 LVH+ patients and compared with 25 age-matched healthy controls and 25 hypertensive patients without LVH (LVH-). Clinical status, diastolic function and BRS were then assessed in LVH+ patients during treatment with telmisartan (monotherapy or combined with hydrochlorothiazide and/or amlodipine) at 6- and 18-month follow-ups. LVH+ patients had significantly altered diastolic function indices and decreased BRS as compared with healthy controls and LVH- patients. During the 18-month follow-up, favorable changes in diastolic function were associated with improvement in BRS at rest and during tilting. In multivariate regression models, an index reflecting rate of LV myocardial relaxation (E'sept) where E'sept denotes peak early diastolic velocity at the septal mitral annulus and a surrogate for LV filling pressure (E/E'sept), independently from other clinical and echocardiographic variables related to the low-frequency component of BRS during tilting. In conclusion, the LV diastolic function indices have independent associations with BRS parameters obtained at rest and during orthostatic stress in LVH+ patients receiving long-term pharmacological intervention.

Combining 3D tracking and surgical instrumentation to determine the stiffness of spinal motion segments: a validation study.

The spine is a complex structure that provides motion in three directions: flexion and extension, lateral bending and axial rotation. So far, the investigation of the mechanical and kinematic behavior of the basic unit of the spine, a motion segment, is predominantly a domain of in vitro experiments on spinal loading simulators. Most existing approaches to measure spinal stiffness intraoperatively in an in vivo environment use a distractor. However, these concepts usually assume a planar loading and motion. The objective of our study was to develop and validate an apparatus, that allows to perform intraoperative in vivo measurements to determine both the applied force and the resulting motion in three dimensional space. The proposed setup combines force measurement with an instrumented distractor and motion tracking with an optoelectronic system. As the orientation of the applied force and the three dimensional motion is known, not only force-displacement, but also moment-angle relations could be determined. The validation was performed using three cadaveric lumbar ovine spines. The lateral bending stiffness of two motion segments per specimen was determined with the proposed concept and compared with the stiffness acquired on a spinal loading simulator which was considered to be gold standard. The mean values of the stiffness computed with the proposed concept were within a range of ±15% compared to data obtained with the spinal loading simulator under applied loads of less than 5 Nm.

Accuracy of navigated surgery of the pelvis after surface matching with an a-mode ultrasound probe.

Computer-aided surgery (CAS) allows for real-time intraoperative feedback resulting in increased accuracy, while reducing intraoperative radiation. CAS is especially useful for the treatment of certain pelvic ring fractures, which necessitate the precise placement of screws. Flouroscopy-based CAS modules have been developed for many orthopedic applications. The integration of the isocentric flouroscope even enables navigation using intraoperatively acquired three-dimensional (3D) data, though the scan volume and imaging quality are limited. Complicated and comprehensive pathologies in regions like the pelvis can necessitate a CT-based navigation system because of its larger field of view. To be accurate, the patient's anatomy must be registered and matched with the virtual object (CT data). The actual precision within the region of interest depends on the area of the bone where surface matching is performed. Conventional surface matching with a solid pointer requires extensive soft tissue dissection. This contradicts the primary purpose of CAS as a minimally invasive alternative to conventional surgical techniques. We therefore integrated an a-mode ultrasound pointer into the process of surface matching for pelvic surgery and compared it to the conventional method. Accuracy measurements were made in two pelvic models: a foam model submerged in water and one with attached porcine muscle tissue. Three different tissue depths were selected based on CT scans of 30 human pelves. The ultrasound pointer allowed for registration of virtually any point on the pelvis. This method of surface matching could be successfully integrated into CAS of the pelvis.

[A-mode ultrasonic pointer for navigated pelvic surgery]. / A-Mode-Ultraschall-Pointer für die navigierte Beckenchirurgie.

Surgical navigation has proven to be a minimally invasive procedure that enables precise surgical interventions with reduced exposure to irradiation for patient and personnel. Fluoroscopy-based modules have prevailed on the market. For certain operations of the pelvis computed tomography is necessary with its high imaging quality and considerably larger scan volume. To enable navigation in these cases, matching of the CT data set and the patient's real pelvic bone is essential. The common pair point-matching algorithm is complemented by the surface-matching algorithm to achieve an even higher overall precision of the system. For conventional surface matching with a solid pointer, the bone has to be exposed from soft tissue quite extensively, using a solid pointer. This conflicts with the claim of computer-assisted surgery to be minimally invasive. We integrated an A-mode ultrasonic pointer with the intention to perform extended surface matching on the pelvic bone noninvasively. Related to the conventional method, comparable and to some extent even improved precision conditions could be established.

Development and psychometric validation of the HIV Treatment Knowledge Scale.

Accurate treatment knowledge is required for patients to successfully manage complex medical conditions. Existing HIV knowledge scales focus on disease transmission and risk factors. This is the first study to develop and validate a scale to measure HIV treatment knowledge about complex treatment issues such as adherence, side-effects and drug resistance. A total of 346 participants were recruited into this cross-sectional study. Participants included HIV-positive patients (n=130), HIV-hepatitis C co-infected patients (n=22), hepatitis C patients, (n=78), community healthcare providers (n=35) and college students (n=81). Participants completed the proposed HIV Treatment Knowledge Scale and a validated measure of general knowledge about HIV transmission and risk factors. Two-week test-retest data were collected. Results demonstrated that the HIV Treatment Knowledge Scale was significantly correlated with general HIV knowledge across all samples. Among HIV-positive patients, the HIV Treatment Knowledge Scale was positively associated with time since HIV diagnosis. HAART-experienced patients had significantly higher treatment knowledge than HAART-naïve patients. HIV-positive patients scored significantly higher than hepatitis C patients and college students on HIV treatment knowledge. Test-retest reliability (r=0.83) and internal consistency (reliability coefficient=0.90) were both satisfactory. The HIV Treatment Knowledge Scale is a novel, easy-to-administer measure demonstrating high levels of validity and reliability. It has important applications as a clinical teaching tool with patients and healthcare workers and it could be used as an outcome indicator in HIV educational intervention studies.

Accuracy considerations in navigated cup placement for total hip arthroplasty.

Computer assisted orthopaedic surgery (CAOS) technology has recently been introduced to overcome problems resulting from acetabular component malpositioning in total hip arthroplasty. Available navigation modules can conceptually be categorized as computer tomography (CT) based, fluoroscopy based, or image-free. The current study presents a comprehensive accuracy analysis on the computer assisted placement accuracy of acetabular cups. It combines analyses using mathematical approaches, in vitro testing environments, and an in vivo clinical trial. A hybrid navigation approach combining image-free with fluoroscopic technology was chosen as the best compromise to CT-based systems. It introduces pointer-based digitization for easily assessable points and bi-planar fluoroscopy for deep-seated landmarks. From the in vitro data maximum deviations were found to be 3.6 degrees for inclination and 3.8 degrees for anteversion relative to a pre-defined test position. The maximum difference between intraoperatively calculated cup inclination and anteversion with the postoperatively measured position was 4 degrees and 5 degrees, respectively. These data coincide with worst cases scenario predictions applying a statistical simulation model. The proper use of navigation technology can reduce variability of cup placement well within the surgical safe zone. Surgeons have to concentrate on a variety of error sources during the procedure, which may explain the reported strong learning curves for CAOS technologies.

A randomized controlled psycho-education intervention trial: Improving psychological readiness for successful HIV medication adherence and reducing depression before initiating HAART.

The purpose of this study was to evaluate a novel psycho-educational intervention intended to increase patients' medication preparedness and treatment adherence skills before initiating highly active antiretroviral therapy (HAART). Sixty-three HIV-positive patients not currently on antiretroviral therapy participated in a randomized controlled trial of a standardized, four-session psycho-educational intervention (Supportive Therapy for Adherence to Antiretroviral Treatment; STAART). Session topics included learning techniques to increase medication adherence and learning effective strategies to cope with stress and depression. Patients completed psychological questionnaires assessing psychological readiness to initiate HAART and depressed mood. They completed both measures at study baseline and at four-weeks post-baseline. After controlling for baseline medication readiness scores, intervention patients (n = 30) reported significantly higher mean medication readiness following the STAART intervention (four-weeks post-baseline) (27.3+/-6.9) compared to controls (n = 33; 24.6+/-9.9; p < 0.05). Among depressed patients (n = 27), those receiving the intervention (n = 15) reported significantly lower mean depression scores at four-weeks post-baseline (22.5+/-12.9) compared to controls (n = 12; 27+/-9.9; p < 0.05). The STAART intervention enhanced HIV treatment readiness by better preparing patients prior to initiating HAART. It was also beneficial for reducing depressive symptoms in depressed, HIV-positive patients.

QT interval dispersion as a new marker of restenosis after percutaneous transluminal coronary angioplasty of isolated single-vessel coronary artery stenosis.

BACKGROUND: There are no reliable non-invasive markers of restenosis after percutaneous transluminal coronary angioplasty (PTCA). The aim of our study was to measure changes in QT interval dispersion after PTCA and to determine whether restenosis subsequently affects QT interval dispersion. METHODS AND RESULTS: Fifty-six consecutive patients - 41 men and 15 women (mean age: 56.2 +/-8.3 years) - with isolated stenosis of the left anterior descending artery who underwent successful PTCA were studied. A symptom-limited treadmill exercise test was performed within 7 days after PTCA and then again before repeated angiography. Repeated coronary angiography revealed restenosis in 15 patients (26.8%) and no signs of significant stenosis in 41 patients (73.2%). QT interval dispersion in the group of patients with restenosis measured before exercise increased from baseline 34 +/- 7 to 49 +/- 15 ms after 6 months (p < 0.01) and QT interval dispersion measured immediately after exercise increased from baseline 38 +/- 4 to 68 +/- 21 ms after 6 months (p < 0.001). In contrast, patients without restenosis showed no significant changes in QT interval dispersion measured before (baseline: 34 +/- 9 ms; after 6 months 33 +/- 12 ms; p = NS) and immediately after exercise (baseline: 34 +/- 12 ms; after 6 months: 33 +/- 10; p = NS). When QT interval dispersion > or =60 ms (measured 6 months after PTCA procedure) was considered as a potential marker of restenosis, this indicator had very high sensitivity and specificity when measured immediately after exercise (80 and 95% respectively). CONCLUSIONS: QT interval dispersion significantly increases in the group of patients with documented restenosis and may be a simple, non-invasive marker of restenosis. However, further studies are needed to confirm this observation.

Kinetic analysis and subambient temperature on-line on-column derivatization of an active aldehyde.

The chromatographic analysis of aldehydes under typical reversed-phase conditions may be a challenging task due to an equilibrium process leading to the formation of a gem diol species regardless of acidic or basic conditions. Initially, a reversed-phase HPLC gradient elution was developed to determine the amount of a n acetylenic aldehyde in a reaction mixture. Significant fronting was observed under acidic and basic conditions even at -5 degrees C. In order to circumvent this problem, a reversed-phase HPLC gradient method on a C18 column at subambient temperature was developed using diethylamine as a mobile phase additive for on-line on-column derivatization of the aldehyde moiety. The on-line on-column reaction rate for the derivatization of the aldehyde with diethylamine was determined as a function of column temperature. An Arrhenius plot was constructed and the activation energy was calculated. The chromatographic behavior of the derivatized acetylenic aldehyde and products formed in-situ in the chromatographic system were studied at various temperatures ranging from -10 to 60 degrees C. It was found that the reaction products could be controlled by adjusting the column temperature. Different reaction pathways were identified as a function of temperature. The products and the reaction pathways were characterized by NMR, LC-MS and UV spectra.

Mechanistic aspects of chiral discrimination on an amylose tris(3,5-dimethylphenyl)carbamate.

The separation of [2R-[2alpha(R*),3alpha]]-5-[[2-[1-[3,5-bis-(trifluoromethyl)phenyl]ethoxy]-3(S)-4-fluorophenyl)4-morpholinyl]-methyl]-N,N-dimethyl-1H-1,2,3-triazole-4-methanamine hydrochloride from its enantiomer was achieved on an amylose tris-3,5-dimethylphenyl carbamate stationary phase. The retention of the enantiomers is dominated by weak hydrogen bonds while the enantioselectivity is governed by other kinds of interactions, e.g., inclusion in the amylose carbamate chains. Van't Hoffplots of 1nalpha vs. reciprocal temperature were non-linear and could be divided into two linear regions. One region at low temperature (5 degrees C- approximately 20 degrees C) and another one between 25 degrees C-70 degrees C with the change in slope occurring between 16 degrees C and 20 degrees C. DSC experiments suggested that the behavior can be attributed to breakage of H-bonds triggering a conformational change. Molecular simulation indicated a correlation between the interaction energies and the elution order obtained experimentally. The most retained enantiomer (R,R,S-enantiomer) interacts with the stationary phase through a hydrogen bond between the triazole proton and the C=O groups of the stationary phase, as well as through an inclusion in the cleft of the stationary phase. The other enantiomer exhibits a bifurcated H-bond between the triazolic proton and the C=O groups of the stationary phase leading to a less stable complex.