The Impact of Diabetes Mellitus and Admission Hyperglycemia on Clinical Outcomes after Recanalization Therapies for Acute Ischemic Stroke: STAY ALIVE National Prospective Registry.

It was previously reported that diabetes mellitus (DM) and admission hyperglycemia (aHG) were associated with poor clinical outcomes in patients with acute ischemic stroke (AIS) who were treated with intravenous thrombolysis (IVT) or mechanical thrombectomy (MT). Our study aimed to assess the prognostic effect of DM and aHG (≥7.8 mmol/L) on clinical outcomes in patients treated with recanalization therapies (IVT and MT). Our multicentric study was based on data from the prospective STAY ALIVE stroke registry between November 2017 and January 2020. We compared the demographic data, clinical parameters and time metrics between recanalized DM and non-DM groups, and we analyzed the impact of DM and aHG on 90-day functional outcome, 90-day mortality, symptomatic intracranial hemorrhage (sICH), and successful recanalization. Statistical analyses were also performed in two subgroups: (1) patients treated with IVT alone and (2) patients treated with MT. Altogether, we included 695 patients from the three participating stroke centers in Hungary. Regarding the overall population, patients with diabetes were older (72 vs. 67 years, p < 0.001) and comorbidities were more frequent. There were significant differences in the 90-day good functional outcome (48.9% vs. 66.7%, p < 0.001), 90-day mortality (21.9% vs. 11.6%, p < 0.001) and the rate of symptomatic intracranial hemorrhaging (sICH) (7.8% vs. 2.2%, p < 0.001) between the groups. Diabetes and aHG were independently associated with a poor clinical outcome (OR 2.02, 95% CI 1.31−3.11, p = 0.001; OR 2.09, 95% CI 1.39−3.14, p < 0.001) and mortality at 3 months (OR 2.45, 95% CI 1.35−4.47, p = 0.003; OR 2.42, 95% CI 1.37−4.28, p = 0.002) and sICH (OR 4.32, 95% CI 1.54−12.09, p = 0.005; OR 4.61, 95% CI 1.58−13.39, p = 0.005) in the overall population. However, the presence of DM and aHG was not correlated with successful reperfusion (OR 0.39, 95% CI 0.09−1.67, p = 0.205; OR 0.42, 95% CI 0.09−1.97, p = 0.274) after MT. Our study revealed that diabetes and hyperglycemia on admission were correlated with poor clinical outcomes at 3 months in patients with acute stroke regardless of the recanalization method. In addition, the variables were also associated with sICH after recanalization therapies. However, successful recanalization was not associated with DM and aHG in patients who underwent MT.

Optimization of Large Vessel Occlusion Detection in Acute Ischemic Stroke Using Machine Learning Methods.

The early detection of large-vessel occlusion (LVO) strokes is increasingly important as these patients are potential candidates for endovascular therapy, the availability of which is limited. Prehospital LVO detection scales mainly contain symptom variables only; however, recent studies revealed that other types of variables could be useful as well. Our aim was to comprehensively assess the predictive ability of several clinical variables for LVO prediction and to develop an optimal combination of them using machine learning tools. We have retrospectively analysed data from a prospectively collected multi-centre stroke registry. Data on 41 variables were collected and divided into four groups (baseline vital parameters/demographic data, medical history, laboratory values, and symptoms). Following the univariate analysis, the LASSO method was used for feature selection to select an optimal combination of variables, and various machine learning methods (random forest (RF), logistic regression (LR), elastic net method (ENM), and simple neural network (SNN)) were applied to optimize the performance of the model. A total of 526 patients were included. Several neurological symptoms were more common and more severe in the group of LVO patients. Atrial fibrillation (AF) was more common, and serum white blood cell (WBC) counts were higher in the LVO group, while systolic blood pressure (SBP) was lower among LVO patients. Using the LASSO method, nine variables were selected for modelling (six symptom variables, AF, chronic heart failure, and WBC count). When applying machine learning methods and 10-fold cross validation using the selected variables, all models proved to have an AUC between 0.736 (RF) and 0.775 (LR), similar to the performance of National Institutes of Health Stroke Scale (AUC: 0.790). Our study highlights that, although certain neurological symptoms have the best ability to predict an LVO, other variables (such as AF and CHF in medical history and white blood cell counts) should also be included in multivariate models to optimize their efficiency.

[The role of intravenous thrombolysis before mechanical thrombectomy in the treatment of large vessel occlusion strokes]. / A mechanikus thrombectomiát megelozo intravénás thrombolysis szerepe az akut agyi nagyérelzáródások kezelésében.

BACKGROUND AND PURPOSE: The efficacy of intravenous thrombolysis (IVT) is moderate in the proximal vascular segments of intracranial arteries, as opposed to mecha-nical thrombectomy (MT). In the management of acute ischemic stroke (AIS) caused by large vessel occlusions (LVO), IVT prior to MT is highly recommended based on the latest guidelines, but the necessity of IVT has been questioned by the latest studies of the past years. The aim of our study was to investigate and compare the efficacy and safety of direct mechanical thrombectomy (dMT) and combined therapy (CT) for patients who suffered an AIS with LVO and were treated in our department. METHODS: We investigated patients with AIS caused by LVO who were admitted up to 4.5 hours after symptom onset and underwent MT in our department between November 2017 and August 2019. Patients' data were collected in our stroke register. Patients enrolled in our study were divided into two groups depending on whether dMT or CT was used. Our primary outcome was the 30- and 90- day functional outcome measured by modified Rankin Scale (mRS). Mortality at 30- and 90- day, successful recanalization rates, and symptomatic intracranial hemorrhage were considered as secondary outcomes. RESULTS: A total of 142 patients (age: 68.3 ± 12.6 years, 53.5% female) were enrolled in our study, including 81 (57.0%) dMT cases, and 61 (43.0%) patients who received CT. The vascular risk factors and comorbidities were significantly higher in the dMT-treated group. At day 30, the rate of favorable functional outcomes was 34.7% in dMT vs. 43.6% among those who received CT (p = 0.307), by day 90 this ratio changed to 40.8% vs. 46.3% (p = 0.542). Mortality rates at day 30 were 22.2% and 23.6% (p = 0.851), and at day 90 33.8% and 25.9% (p = 0.343). The rate of effective recanalization was 94.2% for dMT-treated patients and 98.0% for CT-treated patients (p = 0.318). Symptomatic intracranial hemorrhage was detected in 2.5% of dMT-treated patients and 3.4% of CT-treated group (p = 0.757). CONCLUSION: Our results suggest that CT is associated with a moderately better outcome compared to dMT. IVT prior to MT did not increase the risk of symptomatic intracranial hemorrhages.

Comparing Endovascular Treatment Methods in Acute Ischemic Stroke Due to Tandem Occlusion Focusing on Clinical Aspects.

INTRODUCTION: Acute ischemic strokes (AIS) due to tandem occlusion (TO) of intracranial anterior large vessel and concomitant extracranial internal carotid artery (EICA) are represent in 15-20% of all ischemic strokes. The endovascular treatment (EVT) strategy for those patients is still unclear. Although the intracranial mechanical thrombectomy (MT) is considered as a standard treatment approach, the EICA lesion stent necessity remains a matter of debate. We sought to assess the efficacy and safety of EVT in tandem lesions, particularly the EICA stenting management. METHODS: We retrospectively analyzed all patients with anterior circulation stroke associated with EICA lesion and receiving EVT in the three participated stroke centers between November 2017 and December 2020. Patients' data were collected from our prospective stroke registry (STAY ALIVE). Patients enrolled in our study were divided into two groups depending on whether acute carotid stenting (ACS) or balloon angioplasty only (BAO) technique was used. Our primary outcome was the 90-day functional outcome assessed by modified Rankin scale (mRS). Mortality at 90 days and symptomatic intracranial hemorrhage (sICH) were considered as secondary outcomes. RESULTS: A total of 101 patients (age: 67 ± 10 years, 38.6% female) were enrolled in our study, including 29 (28.3%) BAO cases, and 72 (71.3%) patients treated with ACS. Patients in the BAO group were slightly older (70 ± 9 years vs. 66 ± 10 years, p = 0.054), and had higher prevalence of comorbidities such as hypertension (100.0% vs. 59.4%, p < 0.001). There was no significant difference in favorable outcomes (51.7% vs. 54.4%, p = 0.808) between the groups. However, we observed a trend towards higher rates of sICH (8.3% vs. 3.4%, p = 0.382) and 90-day mortality (23.5% vs. 13.8%, p = 0.278) with significantly higher frequency of distal embolization (39.1% vs. 17.9%, p = 0.043) in patients with ACS. In the overall population age (p = 0.013), atrial fibrillation (AF) (p = 0.008), National Institutes of Health Stroke Scale (NIHSS) baseline (p = 0.029), and successful recanalization (p = 0.023) were associated with favorable outcome. CONCLUSION: Endovascular approach of EICA in addition to MT was safe and effective in tandem occlusion of anterior circulation. Furthermore, our results suggest that balloon angioplasty technique without acute stenting shows a comparable favorable outcome rate to ACS with moderately less hemorrhagic events and mortality rates.

Capability of stroke scales to detect large vessel occlusion in acute ischemic stroke - a pilot study.

BACKGROUND AND PURPOSE: Rapid changes of stroke management in recent years facilitate the need for accurate and easy-to-use screening methods for early detection of large vessel occlusion (LVO) in acute ischemic stroke (AIS). Our aim was to evaluate the ability of various stroke scales to discriminate an LVO in AIS. METHODS: We have performed a cross-sectional, observational study based on a registry of consecutive patients with first ever AIS admitted up to 4.5 hours after symptom onset to a comprehensive stroke centre. The diagnostic capability of 14 stroke scales were investigated using receiver operating characteristic (ROC) analysis. RESULTS: Area under the curve (AUC) values of NIHSS, modified NIHSS, shortened NIHSS-EMS, sNIHSS-8, sNIHSS-5 and Rapid Arterial Occlusion Evaluation (RACE) scales were among the highest (>0.800 respectively). A total of 6 scales had cut-off values providing at least 80% specificity and 50% sensitivity, and 5 scales had cut-off values with at least 70% specificity and 75% sensitivity. CONCLUSION: Certain stroke scales may be suitable for discriminating an LVO in AIS. The NIHSS and modified NIHSS are primarily suitable for use in hospital settings. However, sNIHSS-EMS, sNIHSS-8, sNIHSS-5, RACE and 3-Item Stroke Scale (3I-SS) are easier to perform and interpret, hence their use may be more advantageous in the prehospital setting. Prospective (prehospital) validation of these scales could be the scope of future studies.

Teleradiology-based stroke network in Western and Southern Transdanubia in Hungary / Stroke-ellátást támogató teleradiológiai hálózat a Nyugat- és Dél-Dunántúlon.

Összefoglaló. Bevezetés: A stroke kezelésének lehetoségei az utóbbi években jelentosen megváltoztak: a thrombolysis után bevezetésre került a mechanikus thrombectomia, és a terápiás idoablak is jelentosen kitágult az utóbbi évek nagy multicentrikus tanulmányai alapján. Ezek a lehetoségek új igényeket fogalmaztak meg a képalkotó diagnosztikával szemben: az ischaemia okozta morfológiai elváltozások mellett az artériás és a kollaterális rendszer állapotát, valamint bizonyos esetekben az agy szöveti perfúzióját is szükséges meghatározni. Ezeket a komplex kiértékelési feladatokat ma már mesterségesintelligencia-algoritmusok támogathatják, melyek a kiértékelést pár perc alatt elvégezve segítenek a terápiás döntés kialakításában. Célkituzés: A Dél- és a Nyugat-dunántúli régióban hat intézmény részvételével egy dedikált stroke teleradiológiai hálózat kialakítása. Módszer: A stroke-CT-kiértékelo szoftver és a képkommunikáció integrációja, a vizsgálati protokollok technikai paramétereinek egységesítése, a kiértékelési eredmények teleradiológiai megjelenítése valósult meg a hálózat kialakítása során. Eredmények: A hálózat egységesítette nemcsak a stroke-CT-protokollok beállításait, de beutalási és értékelési szempontjait is. A stroke-CT-kiértékelések és a mechanikus thrombectomiák száma is emelkedett az elmúlt egy évben. Következtetés: A dedikált teleradiológiai stroke-hálózat segítségével optimalizálni kívánjuk a régió stroke-ellátását: egyrészt lehetoleg ne maradjanak ellátatlanul a thrombectomiából valószínuleg profitáló betegek, másrészt ne terheljük az ellátórendszert olyan esetekkel, melyekrol a teljes dokumentáció ismeretében derül ki, hogy nem javasolt a beavatkozás. Orv Hetil. 2021; 162(17): 668-675. INTRODUCTION: The possibilities of cerebral stroke management have changed substantially during the last few years. Following a few multicentric studies, mechanical thrombectomy became an established method besides thrombolysis. In addition, the therapeutic window for both methods is much wider now than before. These changes described above demanded more information of CT morphological changes due to ischemia, but the condition and functionality of the arterial and collateral system, and occasionally tissue perfusion performance should also be characterized. Recently, evaluation of different computer tomographic (CT) measurements can be done using artificial intelligence based methods, which perform data analysis in a few minutes. OBJECTIVE: To establish a dedicated stroke teleradiology network with artificial intelligence based image analysis in Western and Southern Transdanubia in Hungary that involves six partner institutes. METHOD: Integration of automated image analysis with teleradiology software was established, and the technical parameters of examination protocols were unified. Results of stroke CT image analysis became accessible through the teleradiology network. RESULTS: The daily use of integrated central image analysis and image communication had a positive impact on referrals and therapeutic evaluation of stroke cases. The number of image processing and mechanical thrombectomy increased during the last year. CONCLUSION: With the help of the dedicated teleradiology stroke network, we want to optimize the stroke care in the region: on the one hand, patients who are likely to benefit from thrombectomy should not be left unattended, on the other, the health care system should not be burdened with cases, when intervention is not recommended having the complete clinical data accessed. Orv Hetil. 2021; 162(17): 668-675.

Relationship between leukocyte counts and large vessel occlusion in acute ischemic stroke.

BACKGROUND: Neuroinflammation plays an important role in the pathogenesis of acute ischemic stroke (AIS) and peripheral leukocyte counts have proved to be independent predictors of stroke severity and outcomes. Clinical significance of large vessel occlusion (LVO) in AIS is increasing, as these patients are potential candidates for endovascular thrombectomy and likely to have worse outcomes if not treated urgently. The aim of our study was to assess the relationship between on admission leukocyte counts and the presence of LVO in the early phase of AIS. METHODS: We have conducted a cross-sectional, observational study based on a registry of consecutive AIS patients admitted up to 4.5 h after stroke onset. Blood samples were taken at admission and leukocyte counts were measured immediately. The presence of LVO was verified based on the computed tomography angiography scan on admission. RESULTS: Total white blood cell (WBC) and neutrophil counts were significantly higher in patients with LVO than those without LVO (P < 0.001 respectively). After adjustment for potential confounders total WBC counts (adjusted OR: 1.405 per 1 × 109/L increase, 95% CI: 1.209 to 1.632) and neutrophil counts (adjusted OR: 1.344 per 1 × 109/L increase, 95% CI: 1.155 to 1.564) were found to have the strongest associations with the presence of LVO. Total WBC and neutrophil counts had moderate ability to discriminate an LVO in AIS (AUC: 0.667 and 0.655 respectively). No differences were recorded in leukocyte counts according to the size of the occluded vessel and the status of collateral circulation in the anterior vascular territory. However, total WBC and neutrophil counts tended to be higher in patients with LVO in the posterior circulation (p = 0.005 and 0.010 respectively). CONCLUSION: Higher admission total WBC and neutrophil counts are strongly associated with the presence of LVO and has moderate ability to discriminate an LVO in AIS. Detailed evaluation of stroke-evoked inflammatory mechanisms and changes according to the presence of LVO demands further investigation.

Detailed severity assessment of Cincinnati Prehospital Stroke Scale to detect large vessel occlusion in acute ischemic stroke.

BACKGROUND: Selecting stroke patients with large vessel occlusion (LVO) based on prehospital stroke scales could provide a faster triage and transportation to a comprehensive stroke centre resulting a favourable outcome. We aimed here to explore the detailed severity assessment of Cincinnati Prehospital Stroke Scale (CPSS) to improve its ability to detect LVO in acute ischemic stroke (AIS) patients. METHODS: A cross-sectional analysis was performed in a prospectively collected registry of consecutive patients with first ever AIS admitted within 6 h after symptom onset. On admission stroke severity was assessed using the National Institutes of Health Stroke Scale (NIHSS) and the presence of LVO was confirmed by computed tomography angiography (CTA) as an endpoint. A detailed version of CPSS (d-CPSS) was designed based on the severity assessment of CPSS items derived from NIHSS. The ability of this scale to confirm an LVO was compared to CPSS and NIHSS respectively. RESULTS: Using a ROC analysis, the AUC value of d-CPSS was significantly higher compared to the AUC value of CPSS itself (0.788 vs. 0.633, p < 0.001) and very similar to the AUC of NIHSS (0.795, p = 0.510). An optimal cut-off score was found as d-CPSS≥5 to discriminate the presence of LVO (sensitivity: 69.9%, specificity: 75.2%). CONCLUSION: A detailed severity assessment of CPSS items (upper extremity weakness, facial palsy and speech disturbance) could significantly increase the ability of CPSS to discriminate the presence of LVO in AIS patients.

Risk analysis of post-procedural intracranial hemorrhage based on STAY ALIVE Acute Stroke Registry.

BACKGROUND: Intracranial hemorrhages (ICH) are classified as symptomatic or asymptomatic according to the presence of clinical deterioration. Here, we aimed to find predictive factors of symptomatic intracranial bleeding in a registry-based stroke research. METHODS: Data of consecutive patients with acute ischemic stroke (AIS) were extracted from the prospective STAY ALIVE stroke registry. Analysis of the total population and treatment sugroups such as endovascular thrombectomy (EVT), intravenous thrombolysis (IVT), or their combination (IVT+EVT) were also done. Outcome measures were ICH, 30- and 90-day clinical outcome based on the modified Rankin Scale (mRS:0-2 as favorable outcome). The hemorrhage was captured by a non-enhanced CT of the skull within 24 h after procedure. RESULTS: A total of 355 patients (mean age: 68±11; female N=177 (49.9%); EVT n=131 (36.9%); IVT n=157 (44.2%); IVT+EVT n=67 (18.9%) were included in the analysis. The total number of ICH was 47 (13%), symptomatic (sICH) 12 (3.4%) and asymptomatic (aICH) 35 (9.9%) in the whole population. NIHSS ≥15.5 at 24 post stroke hours predicted sICH with a sensitivity of 100% and a specificity of 92% (p<0.001). Furthermore, lower age, good collateral circulation on initial CT angiography and lower NIHSS score measured at 24 h independently associated with a favorable 90-day outcome, whereas baseline NIHSS and ASPECT score were not. CONCLUSION: Although partial recanalization, ASPECT< 6, and poor collaterals were significantly associated with sICH, the only independent predictor was NIHSS ≥15.5 at 24 post stroke hours. This suggests a careful evaluation of patients with worsening NIHSS despite an adequate therapy.

Structure and stability of warfarin-sodium inclusion complexes formed with permethylated monoamino-ß-cyclodextrin.

Inclusion complexes of warfarin enantiomers with permethylated monoamino-ß-cyclodextrin (PMMABCD) were characterized using CE and (1)H NMR spectroscopy in aqueous solution. These techniques gave complementary information on the stability and the structure of the diastereomeric host-guest inclusion complexes. The stability constants were determined from CE experiments in a wide pH range. Change in the migration order on the variation of the pH was observed. (1)H NMR assignments have been established for the seven non-equivalent carbohydrate units of the host in the complex at pH 7-9. Specific H-H distance restraints were obtained from NOESY experiments and were introduced into molecular modeling to establish the geometry of the inclusion complexes. It was found that the open side chain warfarin enters the cavity from the primary side of the CD. The orientation of the coumarin ring within the cavity has the same preference for the two warfarin enantiomers owing to an ionic interaction with the amino group of the CD. Accordingly, enantioselectivity at pH 8.5 arises from the difference in the CH/π interactions between warfarin aromatics and the manifold of CH groups of the CD.

Preparation, purification, and characterization of aminopropyl-functionalized silica sol.

A new, simple, and "green" method was developed for the surface modification of 20 nm diameter Stöber silica particles with 3-aminopropyl(diethoxy)methylsilane in ethanol. The bulk polycondensation of the reagent was inhibited and the stability of the sol preserved by adding a small amount of glacial acetic acid after appropriate reaction time. Centrifugation, ultrafiltration, and dialysis were compared in order to choose a convenient purification technique that allows the separation of unreacted silylating agent from the nanoparticles without destabilizing the sol. The exchange of the solvent to acidic water during the purification yielded a stable colloid, as well. Structural and morphological analysis of the obtained aminopropyl silica was performed using transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential measurements, Fourier-transform infrared (FTIR), (13)C and (29)Si MAS nuclear magnetic resonance (NMR) spectroscopies, as well as small angle X-ray scattering (SAXS). Our investigations revealed that the silica nanoparticle surfaces were partially covered with aminopropyl groups, and multilayer adsorption followed by polycondensation of the silylating reagent was successfully avoided. The resulting stable aminopropyl silica sol (ethanolic or aqueous) is suitable for biomedical uses due to its purity.

Synthesis of atropisomeric 1-phenylpyrrole-derived amino alcohols: new chiral ligands.

An efficient synthetic method has been developed for the preparation of a new family of atropisomeric amino alcohols with 1-phenylpyrrole backbone. The synthesis is based on the different reactivities of the two carboxylic groups in optically active 1-[2-carboxy-6-(trifluoromethyl)phenyl]-1H-pyrrole-2-carboxylic acid (1). The chemical structures of the key intermediates were confirmed by spectroscopic methods and single crystal X-ray diffraction measurements. The very first application of a new optically active amino alcohol as catalyst for the enantioselective addition of diethylzinc to benzaldehyde demonstrated the practical usefulness of atropisomeric compounds in which there are six-atom chains between the two functional groups.

Internal motions and exchange processes in human ileal bile acid binding protein as studied by backbone (15)N nuclear magnetic resonance spectroscopy.

Human ileal bile acid binding protein (I-BABP), a member of the family of intracellular lipid binding proteins, is thought to play a role in the enterohepatic circulation of bile salts. Previously, we have shown by stopped-flow fluorescence analysis that positive binding cooperativity exhibited by I-BABP in its interactions with glycocholate (GCA) and glycochenodeoxycholate (GCDA), the two primary bile salts in humans, is related to a slow conformational change in the protein. In this study, we used backbone (15)N relaxation nuclear magnetic resonance (NMR) techniques to obtain residue-specific information about the internal dynamics of apo I-BABP and the doubly ligated I-BABP:GCA:GCDA complex on various time scales. According to our NMR data, bile salt binding is accompanied by a slight rigidification of the (15)N-(1)H bond vectors on the picosecond to nanosecond time scale, with most pronounced changes occurring in the C-D region. In contrast to the minor effects of ligation on fast motions, relaxation dispersion NMR experiments indicate a marked difference between the two protein states on the microsecond to millisecond time scale. In the apo form, an extensive network of conformational fluctuations is detected throughout segments of the EFGHIJ ß-strands and the C-D loop, which cease upon complexation. Our NMR data are in agreement with a conformational selection model we proposed earlier for I-BABP and support the hypothesis of an allosteric mechanism of ligand binding. According to the NMR measurements, the helical cap region may have a less crucial role in mediating ligand entry and release than what has been indicated for fatty acid binding proteins.

Active conformation in amine-thiourea bifunctional organocatalysis preformed by catalyst aggregation.

Self-activation: Takemoto's catalyst gains access to its active conformation by equilibrating between its hydrogen-bonded intra- and intermolecular interactions in apolar aprotic solvents. By destabilization of the inactive monomeric conformations, the extended anti-anti thiourea conformation is preformed in the assembly. On leaving the assembly, this transient conformation has a structural preference to become a catalytically active monomeric species that has the potency for dual activation (see scheme).

Assessing toxicity of polyamidoamine dendrimers by neuronal signaling functions.

We report for the first time on neuronal signaling for the evaluation of interactions between native plasmamembrane and polyamidoamine (PAMAM) dendrimers. Generation 5 polycationic (G5-NH(2)), novel ß-D-glucopyranose-conjugated G5-NH(2) and generation 4.5 polyanionic (G4.5-COONa) polyamidoamine (PAMAM) dendrimers (1-0.0001 mg/ml) were applied in acute brain slices. Functional toxicity assessments-validated by fluorescence imaging of dead cells-were performed by employing electrophysiological indicators of plasma membrane breakdown and synaptic transmission relapse. Irreversible membrane depolarization and decrease of membrane resistance predicted substantial functional neurotoxicity of unmodified G5-NH(2), but not of the G4.5-COONa PAMAM dendrimers. Model calculations suggested that freely moving protonated NH(2) groups of terminal monomeric units of PAMAM dendrimers may be able directly destroy the membrane or inhibit important K(+) channel function via contacting the positively charged NH(2). In accordance, conjugation of surface amino groups by ß-D-glucopyranose units reduced functional neurotoxicity that may hold great potential for biomedical applications.

Catalytic hydrogenation with frustrated Lewis pairs: selectivity achieved by size-exclusion design of Lewis acids.

Catalytic hydrogenation that utilizes frustrated Lewis pair (FLP) catalysts is a subject of growing interest because such catalysts offer a unique opportunity for the development of transition-metal-free hydrogenations. The aim of our recent efforts is to further increase the functional-group tolerance and chemoselectivity of FLP catalysts by means of size-exclusion catalyst design. Given that hydrogen molecule is the smallest molecule, our modified Lewis acids feature a highly shielded boron center that still allows the cleavage of the hydrogen but avoids undesirable FLP reactivity by simple physical constraint. As a result, greater latitude in substrate scope can be achieved, as exemplified by the chemoselective reduction of α,ß-unsaturated imines, ketones, and quinolines. In addition to synthetic aspects, detailed NMR spectroscopic, DFT, and (2)H isotopic labeling studies were performed to gain further mechanistic insight into FLP hydrogenation.

Enantiomeric separation of antimalarial drugs by capillary electrophoresis using neutral and negatively charged cyclodextrins.

Capillary electrophoresis (CE) methods for chiral resolution of five antimalarial drugs (primaquine, tafenoquine, mefloquine, chloroquine and quinacrine) were developed by using a wide selection of neutral and anionic cyclodextrin (CD) derivatives. The use of sulfobutyl-ß-CD and carboxymethyl-ß-CD (CMBCD) resulted in good resolution of quinacrine and tafenoquine, respectively. New results are presented for resolutions of chloroquine and mefloquine. Application of carboxyalkyl- and sulfobutyl-CD derivatives provided improved resolution for primaquine. The impurity in primaquine sample detected by CE was identified as quinocide by MS and NMR. CMBCD provided not only the best separation of primaquine from quinocide but also the simultaneous complete resolution of both compounds.

Inclusion complex formation of sanguinarine alkaloid with cucurbit[7]uril: inhibition of nucleophilic attack and photooxidation.

The inclusion of sanguinarine, a biologically active natural benzophenanthridine alkaloid, in cucurbit[7]uril (CB7) was studied by NMR and ground-state absorption spectroscopy, as well as steady-state and time-resolved fluorescence measurements in aqueous solution. The iminium form of sanguinarine (SA(+)) produces very stable 1 : 1 inclusion complex with CB7 (K = 1.0 × 10(6) M(-1)), whereas the equilibrium constant for the binding of the second CB7 is about 3 orders of magnitude smaller. Marked fluorescence quantum yield and fluorescence lifetime enhancements are found upon encapsulation of SA(+) due to the deceleration of the radiationless deactivation from the single-excited state, but the fluorescent properties of 1 : 1 and 1 : 2 complexes barely differ. The equilibrium between the iminium and alkanolamine forms is shifted 3.69 pK unit upon addition of CB7 as a consequence of the preferential encapsulation of the iminium form and the protection of the 6 position of sanguinarine against the nucleophilic attack by hydroxide anion. On the basis of thermodynamic cycle, about 225 M(-1) is estimated for the equilibrium constant of the complexation between the alkanolamine form of sanguinarine (SAOH) and CB7. The confinement in the CB7 macrocycle can be used to impede the nucleophilic addition of OH(-) to SA(+) and to hinder the photooxidation of SAOH.

Self-association promoted conformational transition of (3R,4S,8R,9R)-9-[(3,5-bis(trifluoromethyl)phenyl))-thiourea](9-deoxy)-epi-cinchonine.

The conformational diversity of the (3R,4S,8R,9R)-9-[(3,5-bis(trifluoromethyl)phenyl))-thiourea](9-deoxy)-epi-cinchonine organocatalyst is discussed. Low-temperature NMR experiments confirmed a self-association process, which promotes the quinoline rotation between two intramolecularly hydrogen-bonded monomeric conformers of the catalyst. The balanced population of the coexisting monomeric and dimeric species allowed us to conduct a structural study of a rather complex conformational dynamics of the pure catalyst. The study is extended by a comparison with other members of the bifunctional amine-thiourea organocatalyst family. Changes in the molecular structure of the catalysts influence the interplay between intra- and intermolecular hydrogen bonding, and yield different extent of catalyst self-association. By assessing the conformation of the individual states, we established the thermodynamic model of a self-association promoted conformational transition.