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Octakis-6-guadinidino-γ-cyclodextrin (gguan) hydrochloride in the presence of phosphates crystallises from aqueous solution in the unprecedented form of a superdimer (dimer-within-a-dimer). The self-assembly exposes four circular octa-guanidinium regions that bind and stabilise discrete H-bonded phosphate anion dimers. The small (∼2 nm) gguan-phosphate assembly is preorganised and stable in aqueous solution, as demonstrated by DLS and NMR experiments.

Supramolecular organisation and self-assembly are the pillars of functionality of many nanosystems. The covalent conjugate (6-spirolactam rhodamine B-6-monodeoxy)-β-cyclodextrin ( Rho- β CD ) is assembled as a self-included, rigid nanostructure, identical in the crystal and in aqueous solution, as revealed by detailed X-ray and NMR analyses. Rho- β CD self-assembly is the result of an interesting reaction pathway which partially de-aggregates Rho and disturbs the zwitterion↔spirolactone equilibrium. Rho- β CD is stable at pH 4.6 but displays controllable photoswitching between the coloured, fluorescent, zwitterionic and the colourless, non-fluorescent closed structures, during several iterative cycles. After an initial drop in absorbance, the on-off process continues without further changes under our irradiation conditions, a consequence of the specific self-locked arrangement of Rho in the cavity. Rho-βCD exemplifies a water soluble photoresponsive nanosystem with improved photostability suggesting promising applications in super resolution bioimaging.

Identifying the role of multiple cooperative supramolecular interactions and the working mechanism underlying the formation of sophisticated, well-defined self-assembled architectures is definitely...

Objective: To investigate the association of blood pressure BP excursions, defined as greater than 185 SBP or greater than 105 DBP, with the probability of intracranial hemorrhage (ICH) and worse functional outcomes in patients with acute ischemic stroke (AIS) treated with tissue plasminogen activator (tPA). Methods: We performed a post hoc analysis of the CLOTBUST-ER trial. Serial BP measurements were conducted using automated cuff recording according to the recommended BP protocol guidelines for tPA administration. The outcomes were prespecified efficacy and safety endpoints of CLOTBUST-ER. Results: The mean number of serial BP recordings per patient was 37. Of the 674 patients, 227 (34%) had at least one BP excursion (>185/105 mmHg) during the first 24 h following tPA-bolus. The majority of BP excursions (46%) occurred within the first 75min from tPA-bolus. Patients with at least one BP excursion in the first 24 h following tPA bolus had significantly lower rates of independent functional outcome at 90 days (31 vs. 40.1%, P=0.028). The total number of BP excursions was associated with decreased odds of 24-h clinical recovery (OR=0.88, 95% CI:0.80-0.96), 24-h neurological improvement (OR=0.87, 95% CI: 0.81-0.94), 7-day functional improvement (common OR=0.92, 95% CI: 0.87-0.97), 90-day functional improvement (common OR=0.94, 95% CI: 0.88-0.98) and 90-day independent functional outcome (OR=0.90, 95% CI: 0.82-0.98) in analyses adjusted for potential confounders. DBP excursions were independently associated with increased odds of any intracranial hemorrhage (OR=1.26, 95% CI: 1.04-1.53). Conclusion: BP excursions above guideline thresholds during the first 24 h following tPA administration for AIS are common and are independently associated with adverse clinical outcomes. © 2021 Lippincott Williams and Wilkins. All rights reserved.

In the search for photosensitizers with chemical handles to facilitate their integration into complex drug delivery nanosystems, new, unsymmetrically substituted, water insoluble meso-tetraphenylporphyrin and meso-tetra(m-hydroxyphenyl)porphyrin derivatives bearing one carboxyalkyl side chain were synthesized. Permethyl-β-cyclodextrin (pMβCD) was their ideal monomerizing host and highly efficient shuttle to transfer them into water. New assembly modes of the extremely stable (Kbinding > 1012 M−2) 2:1 complexes were identified. The complexes are photostable and do not disassemble in FBS-containing cell culture media for 24 h. Incubation of breast cancer MCF-7 cells with the complexes results in intense intracellular fluorescence, strongly enhanced in the endoplasmic reticulum (ER), high photokilling efficiency (~90%) and low dark toxicity. pMβCD stands out as a very capable molecular isolator of mono-carboxyalkyl-arylporphyrins that increases uptake and modulates their localization in the cells. The most efficient porphyrins are envisaged as suitable photosensitizers that can be linked to biocompatible drug carriers for photo- and chemo-therapy applications.

Purpose: Toxocariasis is a helminthozoonosis caused by the infection of a human host by the larva of Toxocara spp., predominately involving Toxocara canis and Toxocara cati, which are common nematodes in dogs and cats, respectively. Human transmission occurs through contact with animals or by consumption of food contaminated with parasite’s eggs. The purpose of this article is to review the current knowledge regarding human neurotoxocariasis. Methods: We conducted a systematic review of the existing literature concerning toxocariasis of the nervous system. Results: Clinical spectrum of human toxocariasis varies widely from a subclinical course to significant organ morbidity. Clinical course depends on parasitic load, the migration route of the larvae and host response. Human neurotoxocariasis is a relatively rare entity yet associated with severe sequelae. Manifestations include meningitis (usually eosinophilic), encephalitis, myelitis, cerebellar vasculitis, space-occupying lesion, behavioral abnormalities, and optic neuritis. Even though valid diagnostic criteria are lacking, neurotoxocariasis should be suspected in patients with neurologic symptoms and cerebrospinal fluid (CSF) pleocytosis with eosinophilia, positive serology for anti-Toxocara antibodies, in serum and/or CSF, sterile CSF and clinical improvement after antihelminthic treatment. Neurotoxocariasis is treated by benzimidazole components, most frequently albendazole, corticosteroids, or diethylcarbamazine. Conclusion: Parasite larvae migrate through tissues and are able to reach the nervous system causing neurotoxocariasis. Its clinical spectrum varies and includes myelitis, meningoencephalitis, brain abscess, and vasculitis. Neurotoxocariasis should always be suspected in patients with neurologic symptoms accompanied by eosinophilia in blood and/or CSF. Early diagnosis and treatment could prevent long-term neurologic impairment. © 2020, Witold Stefański Institute of Parasitology, Polish Academy of Sciences.

Endoplasmic reticulum aminopeptidase 2 assists with the generation of antigenic peptides for presentation onto Major Histocompatibility Class I molecules in humans. Recent evidence has suggested that the activity of ERAP2 may contribute to the generation of autoimmunity, thus making ERAP2 a possible pharmacological target for the regulation of adaptive immune responses. To better understand the structural elements of inhibitors that govern their binding affinity to the ERAP2 active site, we cocrystallized ERAP2 with a medium activity 3,4-diaminobenzoic acid inhibitor and a poorly active hydroxamic acid derivative. Comparison of these two crystal structures with a previously solved structure of ERAP2 in complex with a potent phosphinic pseudopeptide inhibitor suggests that engaging the substrate N-terminus recognition properties of the active site is crucial for inhibitor binding even in the absence of a potent zinc-binding group. Proper utilization of all five major pharmacophores is necessary, however, to optimize inhibitor potency.

Background: Results of our recently published phase III randomized clinical trial of ultrasound-enhanced thrombolysis (sonothrombolysis) using an operator-independent, high frequency ultrasound device revealed heterogeneity of patient recruitment among centers. Methods: We performed a post hoc analysis after excluding subjects that were recruited at centers reporting a decline in the balance of randomization between sonothrombolysis and concurrent endovascular trials. Results: From a total of 676 participants randomized in the CLOTBUST-ER trial we identified 52 patients from 7 centers with perceived equipoise shift in favor of endovascular treatment. Post hoc sensitivity analysis in the intention-to-treat population adjusted for age, National Institutes of Health Scale score at baseline, time from stroke onset to tPA bolus and baseline serum glucose showed a significant (p < 0.01) interaction of perceived endovascular equipoise shift on the association between sonothrombolysis and 3 month functional outcome [adjusted common odds ratio (cOR) in centers with perceived endovascular equipoise shift: 0.22, 95% CI 0.06–0.75; p = 0.02; adjusted cOR for centers without endovascular equipoise shift: 1.20, 95% CI 0.89–1.62; p = 0.24)]. After excluding centers with perceived endovascular equipoise shift, patients randomized to sonothrombolysis had higher odds of 3 month functional independence (mRS scores 0–2) compared with patients treated with tPA only (adjusted OR: 1.53; 95% CI 1.01–2.31; p = 0.04). Conclusion: Our experience in CLOTBUST-ER indicates that increasing implementation of endovascular therapies across major academic stroke centers raises significant challenges for clinical trials aiming to test noninterventional or adjuvant reperfusion strategies. © The Author(s), 2019.

Identifying the role of multiple cooperative supramolecular interactions and the working mechanism underlying the formation of sophisticated, well-defined self-assembled architectures is definitely a challenging and formidable task in understanding the complexity in chemical systems and engineering the properties of advanced materials. The topological design of multifunctional tectons, capable of self-organizing into patterned supramolecular assemblies comprising stacked aromatic molecules, is of particular importance because it can lead to the predictable emergence of controlled functions with tailored electronic properties. Herein, we provide spectroscopic, structural, and mechanistic insights on metal-ion-mediated self-assembly of a charged, amphiphilic perylene-bisimide (PBI) dimer S into two-dimensional (2D) arrays consisting of parallel columnar PBI stacks with a precise spatial arrangement and pattern behavior, using a readily accessible design strategy. The building block (S), a centrosymmetric PBI homodimer bearing a disulfonated trans-stilbene core, was designed to concurrently feature high complexation directionality with a strong binding affinity through multiple supramolecular interactions. In solvents that efficiently solvate PBI, e.g., chloroform, the zinc ion interacts strongly through electrostatic interactions with the negatively charged core of S, and with the πcloud of the stilbene moiety (cation-πinteractions) forming simple 1:1 adducts. In methanol, the findings manifest the efficient formation of well-defined aggregates with H-type excitonic coupling. A single-crystal X-ray structure reveals, despite the sterically crowded bay area of PBIs constituting S, an unprecedented pattern of 2D arrays comprising face-to-face, slipped π-stacked PBI interdimers that pack in parallel columns. This molecular arrangement explains the quenched fluorescence in solution, as well as the appearance of weak excimer-like fluorescence both in solution and crystals. The spectroscopic and structural findings converge to the conclusion that the development of aggregates in solution proceeds by a cooperative growth process driven by a collection of different supramolecular interactions, i.e., electrostatic (core of S), π-πstacking (terminal PBIs), and multiple C-H···π(bay substituents). A corresponding aggregation model fits satisfactorily the experimental data in solution and allows extracting the association constants and spectra of the equilibrated species. © Copyright © 2019 American Chemical Society.

Background: Pulsed-wave ultrasound increases the exposure of an intracranial thrombus to alteplase (recombinant tissue plasminogen activator), potentially facilitating early reperfusion. We aimed to ascertain if a novel operator-independent transcranial ultrasound device delivering low-power high-frequency ultrasound could improve functional outcome in patients treated with alteplase after acute ischaemic stroke. Methods: We did a multicentre, double-blind, phase 3, randomised controlled trial (CLOTBUST-ER) at 76 medical centres in 14 countries. We included patients with acute ischaemic stroke (National Institutes of Health Stroke Scale score ≥10) who received intravenous thrombolysis (alteplase bolus) within 3 h of symptom onset in North America and within 4·5 h of symptom onset in all other countries. Participants were randomly allocated (1:1) via an interactive web response system to either active ultrasound (2 MHz pulsed-wave ultrasound for 120 min [sonothrombolysis]; intervention group) or sham ultrasound (control group). Ultrasound was delivered using an operator-independent device, which had to be activated within 30 min of the alteplase bolus. Participants, investigators, and those assessing outcomes were unaware of group assignments. The primary outcome was improvement in the modified Rankin Scale score at 90 days in patients enrolled within 3 h of symptom onset, assessed in the intention-to-treat population as a common odds ratio (cOR) using ordinal logistic regression shift analysis. This trial is registered with ClinicalTrials.gov, number NCT01098981. The trial was stopped early by the funder after the second interim analysis because of futility. Findings: Between August, 2013, and April, 2015, 335 patients were randomly allocated to the intervention group and 341 patients to the control group. Compared with the control group, the adjusted cOR for an improvement in modified Rankin Scale score at 90 days in the intervention group was 1·05 (95% CI 0·77–1·45; p=0·74). 51 (16%) of 317 patients in the intervention group and 44 (13%) of 329 patients in the control group died (unadjusted OR 1·24, 95% CI 0·80–1·92; p=0·37) and 83 (26%) and 79 (24%), respectively, had serious adverse events (1·12, 0·79–1·60; p=0·53). Interpretation: Sonothrombolysis delivered by an operator-independent device to patients treated with alteplase after acute ischaemic stroke was feasible and most likely safe, but no clinical benefit was seen at 90 days. Sonothrombolysis could be further investigated either in randomised trials undertaken in stroke centres that are dependent on patient transfer for endovascular reperfusion therapies or in countries where these treatments cannot yet be offered as the standard of care. Funding: Cerevast Therapeutics. © 2019 Elsevier Ltd

The coordination-driven synthesis of a rhomboid cavitand composed of two different Bodipys and its inclusion complex with 1,3,6,8-tetrasulfopyrene via ionic self-assembly was established by X-ray crystallography. Highly efficient and unidirectional intra-host and guest-to-host energy transfer was demonstrated by femtosecond fluorescence spectroscopy.

The enantioselectivity of β-cyclodextrin (β-CD) towards L- and D-N-acetyltryptophan (NAcTrp) has been studied in aqueous solution and the crystalline state. NMR studies in solution show that β-CD forms complexes of very similar but not identical geometry with both L- and D-NAcTrp and exhibits stronger binding with L-NAcTrp. In the crystalline state, only β-CD–L-NAcTrp crystallizes readily from aqueous solutions as a dimeric complex (two hosts enclosing two guest molecules). In contrast, crystals of the complex β-CD–D-NAcTrp were never obtained, although numerous conditions were tried. In aqueous solution, the orientation of the guest in both complexes is different than in the β-CD–L-NAcTrp complex in the crystal. Overall, the study shows that subtle differences observed between the β-CD–L,D-NAcTrp complexes in aqueous solution are magnified at the onset of crystallization, as a consequence of accumulation of many soft host–guest interactions and of the imposed crystallographic order, thus resulting in very dissimilar propensity of each enantiomer to produce crystals with β-CD.

Endoplasmic reticulum aminopeptidases 1 and 2 (ERAP1 and ERAP2) cooperate to trim antigenic peptide precursors for loading onto MHC class I molecules and help regulate the adaptive immune response. Common coding single nucleotide polymorphisms in ERAP1 and ERAP2 have been linked with predisposition to human diseases ranging from viral and bacterial infections to autoimmunity and cancer. It has been hypothesized that altered Ag processing by these enzymes is a causal link to disease etiology, but the molecular mechanisms are obscure. We report in this article that the common ERAP2 single nucleotide polymorphism rs2549782 that codes for amino acid variation N392K leads to alterations in both the activity and the specificity of the enzyme. Specifically, the 392N allele excises hydrophobic N-terminal residues from epitope precursors up to 165-fold faster compared with the 392K allele, although both alleles are very similar in excising positively charged N-terminal amino acids. These effects are primarily due to changes in the catalytic turnover rate (kcat) and not in the affinity for the substrate. X-ray crystallographic analysis of the ERAP2 392K allele suggests that the polymorphism interferes with the stabilization of the N terminus of the peptide both directly and indirectly through interactions with key residues participating in catalysis. This specificity switch allows the 392N allele of ERAP2 to supplement ERAP1 activity for the removal of hydrophobic N-terminal residues. Our results provide mechanistic insight to the association of this ERAP2 polymorphism with disease and support the idea that polymorphic variation in Ag processing enzymes constitutes a component of immune response variability in humans.

Endoplasmic reticulum aminopeptidases ERAP1 and ERAP2 cooperate to trim a vast variety of antigenic peptide precursors to generate mature epitopes for binding to major histocompatibility class I molecules. We report here the first structure of ERAP2 determined at 3.08 Å by X-ray crystallography. On the basis of residual electron density, a lysine residue has been modeled in the active site of the enzyme; thus, the structure corresponds to an enzyme-product complex. The overall domain organization is highly similar to that of the recently determined structure of ERAP1 in its closed conformation. A large internal cavity adjacent to the catalytic site can accommodate large peptide substrates. The ERAP2 structure provides a structural explanation for the different peptide N-terminal specificities between ERAP1 and ERAP2 and suggests that such differences extend throughout the whole peptide sequence. A noncrystallographic dimer observed may constitute a model for a proposed ERAP1-ERAP2 heterodimer. Overall, the structure helps explain how two homologous aminopeptidases cooperate to process a large variety of sequences, a key property of their biological role.

We present herein a host-guest supramolecular system by which we were able to obtain precise control of the stereospecificity of a new and unusual adiabatic photoisomerization reaction capable of restoring reversibly the original configuration. The host-guest system is composed of (a) a naphthalene ring linked centrosymmetrically-via sp(2) hybridized oxygen atoms-with methoxytriethyleneglycol chains (1) and (b) a nanotubular cage formed by four self-assembled face-to-face β-cyclodextrins threaded onto the long "axle" of 1. The compound 1 can exist in distinct cis,cis, cis,trans, and trans,trans conformations that are spectrally distinguishable (see Scheme 1 ). Spectroscopic and kinetic manifestations of the torsional isomerization of 1 in the lowest excited singlet state both in solution and within the tubular cage were investigated. The results provide clear evidence that the compact cavity completely blocks the photoisomerization pathway manifested in common solution (cis,cis* → cis,trans*), allowing observation of stereospecific, volume-conserving turning of the naphthalene ring about the two "quasidouble" bonds C(Naph)-O by φ ≈ 180° (cis,cis* → trans,trans*). The photoisomerization is purely adiabatic, and the encaged molecule restores its original configuration by generating torque thermally, when relaxing to the ground state.

An elementary supramolecular conducting system was constructed using a novel (±)-thioctic acid-functionalized β-cyclodextrin host deposited on a gold (Au) surface and an iridium-bearing guest molecule with biphenyl tails to insert specifically into the cyclodextrin cavity. The resulting supramolecular system was used to investigate remote electron communication between the flat Au surface and the platinum (Pt)/iridium (Ir) tip of a scanning tunnelling microscope. The morphology of the surfaces after successive deposition of host molecules followed by guest molecules was investigated. Formation of features of 2 nm size was shown on the Au surface functionalised with the supramolecular system. I–V spectroscopic analysis of the tunnelling current through this supramolecular layer revealed the relation between the effective barrier height and tunnelling distance. Thus, in the supramolecular host–metallo-guest system, a small increase of conductance is observed, compared to the layer without the guest. This can be attributed to the presence of the Ir-guest, which eventually creates intermediate energy states between the Au substrate and the Pt/Ir tip. Copyright © 2011 John Wiley & Sons, Ltd.

The inclusion complex of a salicylaldehyde Schiff base (anil) in β-cyclodextrin (βCD) is reported for the first time. UV–vis spectroscopic and fluorescence studies show that N -(1-adamantyl)salicylaldimine (ASA), which is thermochromic as a free crystalline compound, becomes photochromic upon encapsulation into βCD. Characterisation of the complex has been performed by NMR spectroscopy in aqueous solution and by UV and fluorescence spectroscopy and powder X-ray diffraction in the crystalline state. The NMR studies indicate host:guest ratio of 1:1 and prove that only the adamantyl moiety of the guest is enclosed into the host cavity, whereas the hydroxyphenyl part is outside. Trials to grow single crystals of the complex produced a novel βCD lattice, which can be rationalized by applying the inclusion mode suggested by NMR spectroscopy. βCD in the crystal lattice seems to act as a medium allowing the cis to trans isomerisation of ASA, a volume-demanding process necessary for the expression of photochromism in this class of molecules. The study demonstrates that βCD nanocavities can lead to supramolecular control of the photochemical behaviour of appropriately designed anils, a property with many potential applications.

Crystallization of glutaric anhydride in the presence of β-cyclodextrin (βCD) from aqueous solution resulted in crystals of the glutaric acid/βCD inclusion complex. The result was verified by NMR spectroscopic experiments, which moreover showed that βCD does not protect glutaric anhydride from hydrolysis. The structure determination by X-ray crystallography revealed a host:guest ratio of 1:1 and crystal packing identical to that of natural βCD, i.e., herring bone packing, as is common for guest molecules of small size. Glutaric acid has partial occupancy in the complex and it is disordered in three positions and conformations inside the cavity. All three conformations are stabilised by: (a) Interactions among its carboxyl groups and the host’s primary side hydroxyls pointing towards the cavity, thus justifying the conformations of the latter and (b) by two water molecules located on either side of the cavity, as well as hydroxyl groups of neighbouring hosts. In all conformations the guest is not extended, oxygen atoms between the two carboxyl groups being within H-bond distance.

In an attempt to gain insight in the mode of inclusion of sulfonylurea hypoglycemic drugs into β-cyclodextrin (βCD), the molecular structures of the inclusion complexes of three such drugs, tolbutamide (TBM), tolazamide (TLZ) and glimepiride (GLP), have been determined for the first time by X-ray crystallography. The drugs share a common moiety, a H-bond forming sulfonylurea group in the middle, flanked by a tolyl-group at one end and an additional hydrophobic group (different in the three drugs) at the other end, GLP being further elongated by a 2-pyrrolidinone moiety at the tolyl end. The structures of the inclusion complexes comprise βCD dimers aligned in channels. The hydrophobic groups enter the cavities of two adjacent βCD dimers from the primary sides, whereas the hydrophilic sulfonylurea moiety is located in-between, forming H-bonds with the hosts without disturbing the dimers. In the GLP/βCD complex, the pyrrolidinone extension threads the βCD cavity and emerges from the secondary side. These results are supported by NMR 2D ROESY spectra in aqueous solutions. The extended length of GLP imposes a change in the crystal packing placing the βCD dimers further apart. However, the overall inclusion mode of the three drugs is the same, thus a common inclusion and crystallization process is proposed for sulfonylurea drugs. The structures of the complexes explain the effects of complexation on dissolution, bioavailability and hypoglycemic activity.

The binding of α-, β-, and γ-per(6-guanidino-6-deoxy)cyclodextrins (ag, bg, and gg, respectively) with nucleotides (5′-dAMP, 5′-AMP, and 5′-dCMP) and nucleosides (2′-dA and 2′-dC) was studied with NMR spectroscopy in aqueous solution. Nucleotides formed strong complexes with bg and gg (not ag) through ditopic binding. Multiple Coulombic attractive forces between the guanidino groups and the single phosphate group of the nucleotides drove inclusion of the entire ribose ring into the cavity, in both deoxy- and ribonucleotides, whereas the base moiety was only partially included. In contrast, no interaction was observed between guanidino cyclodextrins and nucleosides. The prevailing stoichiometries in all nucleotide/bg and nucleotide/gg complexes were 1:2, except for 5′-dAMP/bg where oligomeric aggregates formed. The anti orientation of the nucleotides was preserved upon inclusion. The populations of conformers due to ribose pucker, 2′-endo (S) and 3′-endo (N), were practically undisturbed by inclusion. Interestingly, in the nucleotide/bg complexes at 278 K two nucleotide conformers were observed with distinctly different signals in slow mutual exchange owing to cavity restriction and a slow ribose pucker rate, which resulted in the observation of 3′-endo (N) conformer separate from 2′-endo (S) conformer for the first time.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

International audience; The crystal structures of the C57A and V13G molecular variants of Allochromatium vinosum 2[4Fe–4S] ferredoxin (AlvinFd) and that of the homologous ferredoxin from Escherichia coli (EcFd) have been determined at 1.05-, 1.48-, and 1.65-Å resolution, respectively. The present structures combined with cyclic voltammetry studies establish clear effects of the degree of exposure of the cluster with the lowest reduction potential (cluster I) towards less negative reduction potentials (E°). This is better illustrated by V13G AlvinFd (high exposure, E° = −594 mV) and EcFd (low exposure, E° = −675 mV). In C57A AlvinFd, the movement of the protein backbone, as a result of replacing the noncoordinating Cys57 by Ala, leads to a +50-mV upshift of the potential of the nearby cluster I, by removal of polar interactions involving the thiolate group and adjustment of the hydrogen-bond network involving the cluster atoms. In addition, the present structures and other previously reported accurate structures of this family of ferredoxins indicate that polar interactions of side chains and water molecules with cluster II sulfur atoms, which are absent in the environment of cluster I, are correlated to the approximately 180–250 mV difference between the reduction potentials of clusters I and II. These findings provide insight into the significant effects of subtle structural differences of the protein and solvent environment around the clusters of [4Fe–4S] ferredoxins on their electrochemical properties.

Planar nanodevices, consisted of gold electrodes in the nanometer scale fabricated by a conventional e-beam lithography and lift-off process and functionalized by suitably synthesized cyclodextrin-based self-assembled monolayers were electrically characterized. The monolayers were supramolecularly connected to gold nanoparticles, so that the electrodes were bridged. Thus, conductive paths through the cyclodextrin molecules (ideally Au contact/molecule/Au bridge/molecule/Au contact) were formed. In order to study the electrical behaviour of the various samples, different arrangements were used, varying in the cyclodextrin derivative exploited, the way the CD molecules were connected the underlying gold surface and the association of the gold nanoparticles with the monolayer. Hysteresis effects that can be exploited in molecular memory devices were studied in terms of the type of the cyclodextrin complex. The transport properties as well as the topography of the cyclodextrin monolayers were also investigated by scanning tunnelling microscopy.

Per(6-guanidino-6-deoxy)-cyclodextrins , and are novel derivatives, resulting from homogeneous introduction of the guanidino group at the primary side of alpha-, beta- and gamma-cyclodextrins. The products were obtained from the corresponding amino derivatives, as direct guanidinylation of the known bromo-cyclodextrins provided mixtures. The new compounds were fully characterized by NMR spectroscopy and other analytical methods, and their interaction with guest molecules was studied. Strong complexation with 4-nitrophenyl phosphate () disodium salt was observed (K(binding) approximately 5 x 10(4) M(-1)), whereas the non-phosphorylated substrate nitrobenzene () formed a very weak complex. 2D ROESY spectra revealed cavity inclusion in both cases, however the orientation of was opposite to that of , such that the phosphate group is oriented toward the primary side facing the guanidine groups. The strong affinity of towards the phosphorylated guest suggested that interaction with DNA was possible. The new compounds were found to completely inhibit the migration of ultra pure calf thymus DNA during agarose gel electrophoresis, whereas no effects were observed with guanidine alone or with the plain cyclodextrins. Further, the condensation of DNA into nanoparticles in the presence of was demonstrated by atomic force microscopy, confirming strong electrostatic interaction between the biopolymer and the multicationic products . The strong guanidine-phosphate interactions between and DNA were therefore attributed to the clustering of the guanidine groups in the primary area of the cyclodextrin. Cavity effects could not be assessed.

Endoplasmic reticulum (ER) aminopeptidases process antigenic peptide precursors to generate epitopes for presentation by MHC class I molecules and help shape the antigenic peptide repertoire and cytotoxic T-cell responses. To perform this function, ER aminopeptidases have to recognize and process a vast variety of peptide sequences. To understand how these enzymes recognize substrates, we determined crystal structures of ER aminopeptidase 2 (ERAP2) in complex with a substrate analogue and a peptidic product to 2.5 and 2.7 A, respectively, and compared them to the apo-form structure determined to 3.0 A. The peptides were found within the internal cavity of the enzyme with no direct access to the outside solvent. The substrate analogue extends away from the catalytic center toward the distal end of the internal cavity, making interactions with several shallow pockets along the path. A similar configuration was evident for the peptidic product, although decreasing electron density toward its C terminus indicated progressive disorder. Enzymatic analysis confirmed that visualized interactions can either positively or negatively impact in vitro trimming rates. Opportunistic side-chain interactions and lack of deep specificity pockets support a limited-selectivity model for antigenic peptide processing by ERAP2. In contrast to proposed models for the homologous ERAP1, no specific recognition of the peptide C terminus by ERAP2 was evident, consistent with functional differences in length selection and self-activation between these two enzymes. Our results suggest that ERAP2 selects substrates by sequestering them in its internal cavity and allowing opportunistic interactions to determine trimming rates, thus combining substrate permissiveness with sequence bias.

The review presents a full library of single-isomer primary rim per-carboxylate- and per-sulfate-α-, -β- and -γ-cyclodextrin (CD) derivatives and their potential for pharmaceutical nanotechnology. Recent advances in cyclodextrin chemistry have enabled robust methods for the synthesis of single-isomer anionic CDs. Numerous nanobio-applications have been already reported for these negatively charged derivatives, which alone or in combination with other biodegradable molecular platforms can become important carriers for targeted drug delivery and release. Specialized applications are also discussed, such as chiral separations, as well as the ability of per-6-carboxylated-cyclodextrins to coordinate with metal cations and especially with lanthanide cations that makes them candidates as contrast agents for Magnetic Resonance Imaging.

The photochromic and thermochromic properties of trans - N , N ′-bis(salicylidene)-1,2-cyclohexanediamine ( 1 ), trans - N , N ′-bis(3,5-dichloro-salicylidene)-1,2-cyclohexanediamine ( 2 ), trans - N , N ′-bis(3,5-di- t -butyl-salicylidene)-1,2-cyclohexanediamine ( 3 ) and trans - N , N ′-bis(2-hydroxy-naphylidene)-1,2-cyclohexanediamine ( 4 ) were investigated by UV and fluorescence spectroscopies in the crystalline state at various temperatures and the molecular structures of 2 and 4 were determined by single-crystal X-ray diffraction. The existence of the two Schiff base groups on a single molecule does not seem to differentiate the chromobehavior of the present compounds (except possibly for 3 ) with respect to the usual Schiff bases of salicylaldehyde. It is suggested that for this class of compounds also, what determines the thermochromic behavior is the enhanced basicity of the nitrogen atom, due the absence of π,π- and n ,π-conjugation with an aryl ring bound to it. The role of the crystal structure in this case is important only in so far as it affects the electron density on the nitrogen atom. Photochromism, however, is structure dependent and requires space for the generation of the photoproduct that involves cis to trans isomerization in the excited state.

The synthesis, purification, and characterization of mono-6-modified-beta-cyclodextrins bearing N-attached o-, m-, and p-aminobenzoic acids (2, 3, and 4, respectively) are presented. The structures in aqueous solution were investigated using one- and two-dimensional NMR spectroscopy. Detailed assignment of the spectra together with intramolecular NOE correlations revealed the way each of the isomeric appendages is positioned relative to the macrocyclic cavity. No self-inclusion is observed. The o-isomer 2 turns inward over the top of the primary side and interacts with specific protons of the substituted glucopyranose unit A and those of a neighboring unit. The m-isomer 3 displays two conformations, where the substituent resides above the primary side in a tilted manner and interacts either with the previous or the next unit. We propose that the carboxyl groups in both 2 and 3 are localized through H-bonding with one or two, respectively, primary hydroxyl groups of the neighboring glucopyranose units. In a similar positioning of the aromatic ring of the p-isomer 4, the hydrophilic carboxyl end is fully exposed to the aqueous environment. The X-ray structure of 4 shows that the solution conformation has evolved such that in the crystalline state, the aromatic moiety is inserted through its carboxyl part inside another CD where it establishes intermolecular H-bonds with inward-turned primary OH groups. Besides this stabilization, 4 forms parallel and antiparallel supramolecular chains in the crystal that are additionally stabilized by direct H-bonds.

A number of regulatory binding sites of glycogen phosphorylase (GP), such as the catalytic, the inhibitor, and the new allosteric sites are currently under investigation as targets for inhibition of hepatic glycogenolysis under high glucose concentrations; in some cases specific inhibitors are under evaluation in human clinical trials for therapeutic intervention in type 2 diabetes. In an attempt to investigate whether the storage site can be exploited as target for modulating hepatic glucose production, alpha-, beta-, and gamma-cyclodextrins were identified as moderate mixed-type competitive inhibitors of GPb (with respect to glycogen) with K(i) values of 47.1, 14.1, and 7.4 mM, respectively. To elucidate the structural basis of inhibition, we determined the structure of GPb complexed with beta- and gamma-cyclodextrins at 1.94 A and 2.3 A resolution, respectively. The structures of the two complexes reveal that the inhibitors can be accommodated in the glycogen storage site of T-state GPb with very little change of the tertiary structure and provide a basis for understanding their potency and subsite specificity. Structural comparisons of the two complexes with GPb in complex with either maltopentaose (G5) or maltoheptaose (G7) show that beta- and gamma-cyclodextrins bind in a mode analogous to the G5 and G7 binding with only some differences imposed by their cyclic conformations. It appears that the binding energy for stabilization of enzyme complexes derives from hydrogen bonding and van der Waals contacts to protein residues. The binding of alpha-cyclodextrin and octakis (2,3,6-tri-O-methyl)-gamma-cyclodextrin was also investigated, but none of them was bound in the crystal; moreover, the latter did not inhibit the phosphorylase reaction.

Strongly concentration dependent, (1)H NMR chemical shifts of the non-steroidal anti-inflammatory drug acemetacin sodium salt (sodium [[1-(4-chlorobenzoyl)-5-methoxy-2-methylindol-3-yl]acetoxy]acetate), were observed in aqueous solution. Self-titration and nOe experiments, point to a self-association model where stacking takes place via the indole portion of the drug. In addition, conformational isomerism (atropisomerism) of the anti to syn form was confirmed. Further increase of the concentration eventually led to stable chemical shifts and nearly simultaneous appearance of microcrystals. In the presence of betaCD, 1:1 inclusion complexation occurred through the p-chlorobenzoyl part of the drug, whereas with excess betaCD the indole part seemed to participate to a minor degree. The anti isomer is suggested to be involved in the inclusion process. In addition, aggregation of acemetacin was also evident, as competing with the conformational and inclusion equilibria. The present case demonstrates that many competitive processes are simultaneously active in a seemingly simple system. The measurements were strongly dependent upon the pH and use of buffered solutions was mandatory. Finally, for the quantitative analysis of acemetacin in the presence of betaCD, a special HPLC method was developed. The stability of the drug, studied by the identification of the degradation products and the pseudo-first order rate of hydrolysis, was found to be unaffected by the presence of betaCD.

The frequency and temperature dependence of the real (∈') and imaginary (∈'') parts of the dielectric permittivity of the polycrystalline complexβ-cyclodextrin-tridecanoic acid in two hydration forms (with 16.2 and 10.7 water molecules) and β-cyclodextrin-1,13-tridecanedioic acid with 16.4 and 10.5 water molecules have been investigated, in the frequency range 0.1–100 kHz and temperature range 120–310 K. The dielectric behavior is described well by Debye-type relaxation α dispersion. All systems except for the complex of partially dehydrated monocarboxylic acid, exhibit an additional Ω-dispersion, at low frequencies (f < 1000 Hz). Only one-step was found in the ∈' vs. Tplots of both complexes in the two hydration forms, a fact indicating that the watermolecules cannot be divided into strongly bound and easily movable molecules. The∈''vs. T plots, at a fixed frequency (200 Hz), show the characteristic peakattributed to a transition between ordered and disordered β-CD hydroxyl groupsand water molecules. The transition temperature was 202.7 K for all systems examinedexcept for the complex β-CD-tridecanoic acid.16.2 H2O (214.5 K). This means that the order to disorder transformation process was unaffected by the dehydration process in the case of the dicarboxylic acid complex, whereas in the case of the monocarboxylic acid, it was unexpectedly facilitated. The relaxation time varies with temperature, in a Λ like curve (in the range 8–14 μs), with maximum values located at the corresponding order-disorder transition temperatures. The activation energies of the fully hydrated complexes have absolute values of ∼5 kJ/mol in the range 1.98–3.82 KBT transition which are higher than the corresponding values of ∼:2 kJ/mol of the dehydrated complexes. A thermal hysteresis observed in all complexes is a result of the order-disorder transformation.

β-Cyclodextrin forms a 1:1 host:guest inclusion complex ([2]pseudorotaxane) with 4-[2-(4-aminophenyl)ethyl]-benzenamine (1) in water as determined by 1D and 2D NMRexperiments. In the crystalline state, the structure of the complex has revealed a 2:2 stoichiometry, with two βCD molecules forming head-to-head dimers byH-bonds between the secondary O3 hydroxyl groups and enclosing two molecules of the guest. The packing mode of the present complex is encountered for the first time, since it does not belong to any of the four known packing types of the dimeric βCD inclusion complexes. On the other hand,N 1,N 4-bis(4-aminophenyl)-1,4-benzenedimethanamine 2), which is longer than 1 by a phenylene diamine unit, has not afforded any crystals, at present, however it threads into βCD in aqueous solution forming most probably [2]- and [3]pseudorotaxanes. The solution structures and the equilibria in this system are investigated.

Derivatives of 3-O-acetyl-18-βH-glycyrrhetic acid were synthesized. Their structures and membrane activities were studied.

The structure of the β-cyclodextrin-(Z)-tetradec-7-en-1-al complex in aqueous solution and in the solid state, as well as the release profile of the (Z)-tetradec-7-en-1-al (sex pheromone of the olive pest Prays oleae) from the solid complex was investigated, in an effort to correlate the supramolecular structure with the macroscopic property of spontaneous liberation of the pheromone. It was observed that in solution a 2 ∶ 1 host ∶ guest complex prevails, having the guest in a curled configuration. In the crystal structure of the complex, two β-CD molecules forming head-to-head dimers and packed in channels enclose one guest molecule whose methyl terminal aliphatic chain curls at the cis-double bond and runs along the intradimer interface. In the space between host molecules there is also entrapped an additional pheromone molecule, also visible in the IR spectra, which is heavily disordered. The guest inside the cavity is disordered over two sites and exhibits mobility, especially at the methyl and carbonyl end-groups, which is also confirmed by solid state NMR experiments. Thus, there are two types of guest molecules in the crystalline complex, one inside the β-CD cavity and another trapped and held loosely outside the cavity. The release behavior, studied by NMR, shows that the “outside” pheromone is liberated from the solid initially at a fast rate, which reaches very low levels when almost half of the guest molecules have been released. The other half, molecularly encapsulated in the β-CD cavity, is well stabilized.

The structure of the complex of cyclomaltoheptaose (beta-cyclodextrin, betaCD) with 1,14-tetradecanedioic acid has been determined and refined to a final R=0.0693 based on 9824 observed reflections. Each diacid molecule threads through two betaCD monomers arranged in dimers thus, forming a [3]pseudorotaxane. The end carboxylic groups of adjacent dimers, far apart and fully hydrated, are associated indirectly through water molecules. The positioning of the carboxylic groups with respect to the betaCD dimer and the H-bonds with water molecules are very similar to these of the corresponding complexes of the diacids with 12 and 13 carbon atoms. The bending in the middle of the aliphatic chain is more prominent, compared to that of the corresponding guests with less carbon atoms, thus the end carboxylic groups stay in the same height of the primary faces of the betaCD dimeric complex. As a consequence of the present structure, more close contacts are observed between calculated H-atoms of the guest and O-atoms of the host inside the cavity. This bending is allowed by the width of the betaCD dimer cavity at the secondary interface region.

The enantiomers of racemic olive fly sex pheromone 1,7-dioxaspiro[5.5]undecane (1) have been isolated by crystallization with enantiospecific cyclodextrin hosts: (S)-(1) crystallizes with heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TMβCD) and (R)-(1) with hexakis(2,3,6-tri-O-methyl)-α-cyclodextrin (TMαCD). The crystal structure of TMβCD/(S)-(1) from synchrotron radiation data at 100 K, determined for the first time, proves that TMβCD crystallizes with only the (S)-enantiomer from the racemic mixture. Comparison with the 100 K structure of TMαCD/(R)-(1) redetermined with synchrotron data has provided insight into the interactions between each of the hosts with the corresponding enantiomeric guests. Owing to the high resolution of the data and the unusually high quality of the crystals, localization of the H atoms has been achieved, a rare accomplishment for cyclodextrin X-ray structures. This made possible, apart from the geometry of the complexes, the detailed description of a five-membered-ring water cluster with very well ordered hydrogen bonding. The enantiospecificity exhibited by the described systems reveals the subtle differences of the weak intermolecular forces involved in the selective binding of the two optical antipodes by the two hosts. The binding geometry in the two complexes is different, but it is effected in both by numerous host–guest C—H...O interactions, resulting from induced fit of the hosts toward each of the enantiomeric guests. In TMαCD/(R)-(1) two of these H...O host–guest distances, directed toward the acetal O atoms defining the chirality of the guest, are much shorter than the rest and also shorter than all the H...O distances in TMβCD/(S)-(1). Moreover, (R)-(1) interacts not only with the enclosing host, but with other hosts in the crystal lattice, in contrast to (S)-(1) in the TMβCD/(S)-(1) complex which is isolated inside channels formed by the host molecules. The above differences are reflected in the much higher binding constant of TMαCD/(R)-(1) compared with that of TMβCD/(S)-(1) (∼6800 and ∼935 M−1, respectively), determined by NMR in aqueous solution, and the ability of TMαCD to selectively precipitate (R)-(1) from racemic (1) in much higher yield than TMβCD precipitates (S)-(1).

The structure of the complex of beta-cyclodextrin (cyclomaltoheptaose) with beta-naphthyloxyacetic acid was studied in solid state by X-ray diffraction and in aqueous solution by 1H NMR spectroscopy. The complex crystallizes in the channel mode, space group C2, with a stoichiometry of 2:1; two beta-cyclodextrin molecules related by a twofold crystal axis form dimers, in the cavity of which one guest molecule is found on average. The above stoichiometry indicates one guest per beta-CD dimer statistically oriented over two positions or two guest molecules in pi-pi interactions in half of the beta-CD dimers and the rest of the beta-CD dimers empty. In addition, occupancy of 0.5 for the guest per every beta-CD dimer is in accord with the occupancy of the two disordered primary hydroxyls. These two hydroxyl groups, to which the carboxylic oxygen atoms of the guest are hydrogen bonded, point towards the interior of the beta-CD cavity. In aqueous solution, the 1H NMR spectroscopic study indicated that there is a mixture of complexes with host-guest stoichiometries both 1:1 and 2:1.

A detailed crystal structure study of the dimeric inclusion complex of β-cyclodextrin (βCD) with 1,12-dodecanedioic acid is presented [IUPAC name: β-cyclodextrin–1,12-dodecanedioic acid (2/1)]. The structure was solved with synchrotron high-resolution data (0.65 Å) at 100 K [crystal data: P1, Z = 1, a = 18.153 (7), b = 15.456 (8), c = 15.251 (4) Å, α = 102.81 (2), β = 113.13 (2), γ = 99.90 (3)°, V = 3673 (3) Å3, R = 0.0474 for 25 134 unique reflections with I > 2σ(I)]. Moreover, the room-temperature structure is used for comparison [crystal data: P1, Z = 1, a = 18.220 (3), b = 15.488 (3), c = 15.409 (3) Å, α = 102.903 (6), β = 113.122 (5), γ = 99.708 (5)°, V = 3735.2 (12) Å3, R = 0.0828 for 8235 unique reflections with I > 2σ(I)]. Combining the high-resolution data and the low-temperature made possible the location of the disordered guest molecule, 1,12-dodecanedioic acid, inside the wide cavity of the macrocycle formed by two βCD monomers. Moreover, almost all the H atoms of the βCD macrocycle and many of the water molecules have been located in the low-temperature structure. Thus, for the first time, it has been possible to show in detail, up to now only given by neutron diffraction data, that two βCD monomers self-assemble through O3...O3 intermolecular hydrogen bonds to form the βCD dimer, as well as describe the hydrogen-bonding scheme between the dimer's hydroxyl groups among themselves and with water molecules in the lattice. The long guest threads through two host molecules forming a [3]pseudorotaxane. Its polar carboxyl groups, fully hydrated at the primary faces of the βCD dimers, influence their packing so that those faces are exposed to the solvent. This is in contrast to the packing of the β-cyclodextrin complexes of the corresponding aliphatic monoacids, where the dimeric complexes form channels in order to isolate the terminal methyl group from the water environment of the lattice.

The structures of the inclusion complexes of beta cyclodextrin with the aliphatic mono-acids tridecanoic acid (1) and (Z)-tetradec-7-enoic acid (2) have been determined at room temperature. Both compounds crystallise in P1, a = 15.654(6) A, b = 15.650(6) A, c = 15.937(6) A, α = 101.58(1)°, β = 101.59(1)°, γ = 103.58(1)°, Z = 1, for 1 and a = 15.6259(9) A, b = 15.623(1) A, c = 15.935(1) A, α = 101.547(2)°, β = 101.555(2)°, γ = 103.642(2)°, Z = 1, for 2. One molecule of the monoacids threads through two cyclodextrin macrocycles arranged in dimers thus forming [3]pseudorotaxanes. The host dimers are aligned along a channel in order to create a hydrophobic environment for the terminal methyl group of the guest and isolate it from the aqueous environment that surrounds the cyclodextrin dimeric units. The guests exhibit disorder over two orientations resulting in hydrogen bonding between the carboxyl groups of adjacent guest molecules along the channel and formation of carboxylic dimers. This crystal packing differs from that of β-CD complexes of homologous dicarboxylic acids.

The structure of the complex of beta cyclodextrin (βCD) with 1,13-tridecanedioic acid has been determined at low temperature. The compound crystallizes in P1, a = 18.207(6), b = 15.510(5), c = 15.280(6) A, α = 103.02(3), β = 113.13(3), γ = 99.79(3)° and Dc = 1.339 gcm−3 for Z=1. Refinement based on 13134 observed MoKα reflections led to a final R = 0.076. The diacid molecules thread through two βCD arranged in dimers thus, forming [3]pseudorotax-anes. The aliphatic chain of the guest has a few weak, non-bonded interactions with the host inside the long hydrophobic cavity. However, the end carboxyl groups form several strong H-bonds with the solvent in a fashion similar to other βCD/ carboxylic acid complexes that have similar building blocks as the present one: βCD dimers and carboxylic groups of the guest emerging from their two primary faces. Conversely, in the corresponding complexes with aliphatic monocarboxylic acids the carboxyl groups form carboxylic dimers because they are isolated from t...

The frequency and temperature dependence of the real (e') and imaginary (e'') parts of the dielectric constant of polycrystalline complex β-cyclodextrin-4-t-butylbenzyl alcohol [β-CD TERB 11.2H2O] and β-cyclodextrin [β-CD 9.8H2O] and of the corresponding dried forms (β-CD TERB 3.8H2O and β-CD 2.4H2O, respectively) has been investigated, in the frequency range 0-100kHz and temperature range 130-350K. The dielectric behaviour is described well by Debye-type relaxation (α dispersion). All systems except for the βCD TERB 3.8H2O, exhibit an additional Ω dispersion at low frequencies, which usually is attributed to proton transport. In the non-dried samples the temperature dependence of ee' and e''max exhibits two steps, whereas in the dried samples it exhibits only the low temperature step. The low temperature step is due to the tightly bound water molecules, whereas that at higher temperatures is due to easily removable water. The temperature dependence of e'' shows a peak which has been attributed to a trans...

The interactions of 11-aminoundecanoic acid (1), 12-aminododecanoic acid (2), 1,12-diaminododecane (3), and 1,13-tridecanoic diacid (4) with α-cyclodextrin (αCD) were studied in aqueous solution by NMR spectroscopy. The association modes were established with titration and continuous variation plots, variable temperature NMR spectra, and dipolar interactions as recorded in 2D ROESY spectra. The studies were carried out at pH 7.3 and 13.6. These long, linear bifunctional molecules were found to form simultaneously [2]- and [3]pseudorotaxanes with αCD in the aqueous solution. At the higher pH the 1:1 adducts were present at concentrations higher than at the neutral pH. The longer guests formed complexes enriched in the 2:1 constituent at both pH values. There were clear indications that the [2]pseudorotaxanes are present in two isomeric forms. The presence of isomers also in the [3]pseudorotaxanes was not ruled out. Various exchange rate regimes were observed; clearly in neutral solutions the formation of t...

The crystal structure of the 1 : 1 inclusion complex of hexakis(2,3,6-tri-O-methyl)- α-cyclodextrin (TM αCD) with 1,7-dioxaspiro[5.5]undecane (spiroacetal) is orthorhombic, space group C2221, with a = 24.002(2), b = 14.812(1), c = 21.792(2) A V = 7747.3(11) A3 and Z = 8. The molecular six-fold axis of TM αCD coincides with the a two-fold crystallographic axis and the guest is located at the secondary methoxy group side, disordered over two positions related by that axis. The guest model used during the refinement is that of the (R)-enantiomer alone because trials to either refine a 1 : 1 mixture of (R)- and (S)-enantiomers or the (S)-enantiomer alone failed. The crystallographic evidence of enantioselectivity towards the (R)-enantiomer of spiroacetal was confirmed by independent experiments and may be attributed to numerous non bonding interactions between host and guest involving non conventional H-bonds.