Direct investigation of the reorientational dynamics of A-site cations in 2D organic-inorganic hybrid perovskite by solid-state NMR

Limited methods are available for investigating the reorientational dynamics of A-site cations in two-dimensional organic–inorganic hybrid perovskites (2D OIHPs), which play a pivotal role in determining their physical properties. Here, we describe an approach to study the dynamics of A-site cations using solid-state NMR and stable isotope labelling. ²H NMR of 2D OIHPs incorporating methyl-d₃-ammonium cations (d₃-MA) reveals the existence of multiple modes of reorientational motions of MA. Rotational-echo double resonance (REDOR) NMR of 2D OIHPs incorporating ¹⁵N- and ¹³C-labeled methylammonium cations (¹³C,¹⁵N-MA) reflects the averaged dipolar coupling between the C and N nuclei undergoing different modes of motions. Our study reveals the interplay between the A-site cation dynamics and the structural rigidity of the organic spacers, so providing a molecular-level insight into the design of 2D OIHPs.

The reorientational dynamics of A-site cations in two-dimensional organic-inorganic hybrid perovskites play an important role in determining their physical properties. Here the authors use solid state NMR and isotope labelling to reveal multiple modes of reorientational motions of methylammonium cations and the role of structural rigidity of the organic spacers on their dynamics.

Local Deuteration Enables NMR Observation of Methyl Groups in Proteins from Eukaryotic and Cell-Free Expression Systems

Therapeutically relevant proteins such as GPCRs, antibodies and kinases face clear limitations in NMR studies due to the challenges in site-specific isotope labeling and deuteration in eukaryotic expression systems. Here we describe an efficient and simple method to observe the methyl groups of leucine residues in proteins expressed in bacterial, eukaryotic or cell-free expression systems without modification of the expression protocol. The method relies on simple stereo-selective 13 C-labeling and deuteration of leucine that alleviates the need for additional deuteration of the protein. The spectroscopic benefits of "local" deuteration are examined in detail through Forbidden Coherence Transfer (FCT) experiments and simulations. The utility of this labeling method is demonstrated in the cell-free synthesis of bacteriorhodopsin and in the insect-cell expression of the RRM2 domain of human RBM39.

Hydroxamic acid derivatives as histone deacetylase inhibitors: a DFT study of their tautomerism and metal affinities/selectivities

Hydroxamic acids are regarded as potent inhibitors of histone deacetylases (HDAC), and can therefore be used to reduce malignancy growth and size in affected organisms. Although there is a substantial body of information on the structures, syntheses, and biological activities of HDAC inhibitors, several important questions regarding their physicochemical properties and metal affinities/selectivities remain answered. First, how do the conformation and ionization of the hydroxamic group depend on its chemical composition and the dielectric properties of the medium? Second, how do these factors affect the affinities and selectivities of HDAC inhibitors for essential biogenic metal cations? Third, what is the preferred deprotonation site of the hydroxamic moiety and its mode of binding to the metal cation? The present work addressed these questions by performing density functional calculations combined with polarizable continuum model computations. The geometry, deprotonation pattern, metal-binding mode, and metal affinity/selectivity of SAHA, a typical HDAC inhibitor, were examined, and key factors affecting its ligation properties were elucidated. Sulfur- and selenium-containing analogs of SAHA were also modeled for the first time, and their potential as efficient metal-binding entities (to Mg²⁺, Fe²⁺, and Zn²⁺ cations) was assessed. The present calculations shed light on the thermodynamics of the binding of HDAC inhibitors to metal ions, and suggest techniques for enhancing their metal-ligating properties.

Assessing particle kinematics via template matching algorithms

Template matching algorithms represent a viable tool to locate particles in optical images. A crucial factor of the performance of these methods is the choice of the similarity measure. Recently, it was shown in [Gao and Helgeson, Opt. Express 22 (2014)] that the correlation coefficient (CC) leads to good results. Here, we introduce the mutual information (MI) as a nonlinear similarity measure and compare the performance of the MI and the CC for different noise scenarios. It turns out that the mutual information leads to superior results in the case of signal dependent noise. We propose a novel approach to estimate the velocity of particles which is applicable in imaging scenarios where the particles appear elongated due to their movement. By designing a bank of anisotropic templates supposed to fit the elongation of the particles we are able to reliably estimate their velocity and direction of motion out of a single image.

Mg- and Zn-modified calcium phosphates prepared by biomimetic precipitation and subsequent treatment at high temperature

Powders of magnesium-modified as well as zinc-modified calcium phosphates (Me-β-TCP and HA) with a (Ca(2+)+Mg(2+)+Zn(2+)+Na(+)+K(+))/P ratio of 1.3-1.4 and various Me(2+)/(Me(2+)+Ca(2+)) ratios (from 0.005 to 0.16) were prepared in biomimetic electrolyte systems at pH 8, mother liquid maturation and further syntering at 600-1000°C. Some differences in zinc and magnesium modifications have been prognosed on the basis of thermodynamic modeling of the studied systems and explained by the Mg(2+) and Zn(2+) ion chemical behaviour. The temperature as well as the degree of Zn(2+) and Mg(2+) ions substitutions were found to stabilize the β-TCP structure and this effect was more prononced for zinc. Thus, zinc-modified β-TCP powders consisting of idiomorphic crystals were obtained through sintering of Zn(2+) ion substituted calcium phosphates precursors at 800-1000°C. The Mg(2+) ion substitution leads to obtaining magnesium-modified β-TCP with spherical grains.

Biomimetic transformations of amorphous calcium phosphate: kinetic and thermodynamic studies

The biomimetic synthesis and phase transformation of XRD amorphous calcium phosphate were studied by application of kinetic, chemical and spectral (XRD and IR) methods and thermodynamic simulations. Two SBFs (SBFc and SBFr), differing in their HCO(3)(-) and Cl(-) ion contents, were used in the maturation studies. It has been proven that the biomimetic maturation accelerated the phase transformation of less thermodynamically stable amorphous calcium phosphate to poorly crystalline hydroxyapatite. Several regularities have been found: (i) kinetic reasons determined the biomimetic precipitation of XRD-amorphous calcium deficient phosphate (ACP); (ii) the precipitated ACP always contained impurities due to co-precipitation, ion substitution and incorporation phenomena; (iii) the increased content of HCO(3)(-) ions in the surrounding microenvironments increased the rate of phase transformation and the concentration of MeHCO(3)(+) (Me = Ca, Mg) species in the solution, but the solubility of CaCO(3) has only been decreased and its precipitation accelerated, thus playing a crucial role in the process under study.

Cytotoxic Mannich bases of 6-(3-aryl-2-propenoyl)-2(3H)-benzoxazolones

A series of 12 new Mannich bases with chalcone core structure were synthesized as potential antineoplastic agents, via N-aminomethylation of two parent 6-(3-aryl-2-propenoyl)-2(3H)-benzoxazolones. The newly synthesized compounds as well as the chalcone prototypes were evaluated for cytotoxicity in the human pre-B-cell leukemia cell line BV-173 using the MTT-dye reduction assay. The tested compounds exhibited concentration-dependent cytotoxic effects at low micromolar concentrations. Ten of the Mannich bases characterized by significant activity in BV-173 were further evaluated against the chronic myeloid leukemia cell line K-562 and were found to suppress the growth of these cells at relatively higher concentrations as compared to the former tumor model. Selected Mannich bases induced programmed cell death in BV-173 at a concentration of 2.5muM as evidenced by the encountered DNA-laddering. Taken together our data suggest that the presented heterocyclic chalcone derived Mannich bases necessitate detailed pharmacological evaluation in order to define further the structure activity relationships, in a larger spectrum of tumor models and to elucidate the mechanisms implicated in the observed cytotoxic effects.

Inorganic Salt Hydrates as Cryoporometric Probe Materials to Obtain Pore Size Distribution

The depression of the melting temperature of Zn(NO3)2.6H2O was used to obtain the pore size distributions in controlled pore glasses. Measured by 1H NMR, the average value of the temperature depression DeltaT and the known average pore size yield K=DeltaT.d approximately 116 K.nm as the material-dependent factor for Zn(NO3)2.6H2O in the Gibbs-Thompson equation. The melting temperature is close to room temperature. Hence, this salt hydrate and some related other ones are better materials than water (K approximately 50 K.nm) for cryoporometric studies of systems with hydrophilic pores. The data also provide 46 mN/m for the solid-liquid surface tension of this salt hydrate.

Experimental determination of dust-particle charge in a discharge plasma at elevated pressures

The charge of dust particles is determined experimentally in a bulk dc discharge plasma in the pressure range 20-100 Pa. The charge is obtained by two independent methods: one based on an analysis of the particle motion in a stable particle flow and another on an analysis of the transition of the flow to an unstable regime. Molecular-dynamics simulations of the particle charging for conditions similar to those of the experiment are also performed. The results of both experimental methods and the simulations demonstrate good agreement. The charge obtained is several times smaller than predicted by the collisionless orbital motion theory, and thus the results serve as an experimental indication that ion-neutral collisions significantly affect particle charging.

Kinetic measurements of shock wave propagation in a three-dimensional complex (dusty) plasma

"Complex plasmas" consist of electrons, ions, and charged microparticles. The latter are individually observable, allowing kinetic measurements in plasmas. Using a sudden gas pulse, a traveling perturbation was initiated in such a complex plasma and its propagation, acceleration, and steepening-possibly into a shock was followed. The experiment was performed in the PKE-Nefedov laboratory under microgravity conditions on the international space station, i.e., in a complex plasma cloud with very little stored (potential or free) energy and thus free of, e.g., parametric instabilities. The perturbation front remained remarkably smooth, with a microroughness of the order of the interparticle distance. The observations are presented and interpreted.

A rapid method of synthesizing the layered titanosilicate JDF-L1

A rapid procedure for synthesis of highly crystalline and pure samples of JDF-L1 without using organics are reactants or templates is described and indexation of the powder X-ray diffraction pattern of this phase is presented.

Dimethyl 2-[[2-(methoxycarbonyl)-1-(methoxycarbonylmethyl)pyrrol-4-yl]methylene]propanedioate

The title compound, C(15)H(17)NO(8), is a pyrrole-ethene derivative with potential biological activity. Although a large part of the molecule is planar, there is no structural evidence for any conjugation push-pull effect across the ethylenic bond, which is usually observed for substituted ethylenes; pi-electron delocalization appears to be restricted to the 2-(methoxycarbonyl)pyrrole moiety.

A comparison of calibrated and non-calibrated 5.07 nylon monofilaments

The study compares the mechanical performance of two types of nylon monofilaments used in testing for the presence of protective sensation in diabetics with peripheral neuropathy. Comparisons of the application force between a group of calibrated and a group of non-calibrated 5.07 nylon monofilaments were conducted to determine the properties of each type of filament. The analysis demonstrated that there was no significant difference in the application force generated between calibrated and non-calibrated nylon monofilaments.

The modified Hohmann bunionectomy: a retrospective review

A retrospective review of 35 modified Hohmann bunionectomies is presented with analysis of objective radiographic and subjective patient questionnaire results. Thirty-five modified Hohmann bunionectomies were performed, on 29 patients over a 6-year period with follow-up ranging from 11 months to 5 years and 11 months. The modification involves resection of a triangular wedge from the first metatarsal, to minimize shortening, and utilizes two points of fixation. In total, 88% of those patients responding to our questionnaire had either excellent or good results. The Hohmann bunionectomy is a valuable procedure in alleviating symptoms caused by hallux abductovalgus.

The durability of the Semmes-Weinstein 5.07 monofilament

Peripheral neuropathy is a risk factor that predisposes diabetic patients to plantar foot ulcerations and lower extremity amputations. Clinicians have searched for a reliable, cost-effective, and simple method in the identification of diabetic patients who are at increased risk of developing plantar foot ulcers. Currently, many diabetic foot clinics utilize the Semmes-Weinstein 5.07/10 g monofilament in this identification process. Ten 5.07 monofilaments were placed in an Instron Dynamic Testing Instrument and their respective filament forces were measured utilizing a Mettler scale after being subjected to repetitive applications. After 500 cycles were performed, there was an average filament force reduction of 1.2 g. After 1,500 cycles, there was still an average reduction of 1.2 g. F-testing and the Duncan test identified a significant difference between filament forces at 0, 500, 1,000, and 1,500 cycles. These data lead to a conclusion that continual utilization of the nylon filaments may lead to a reduced ability to accurately detect peripheral neuropathy and identify those who are at risk for the development of plantar foot ulcerations.

Synthesis and Physicochemical Characterization of a New Gadolinium Chelate: The Liver-Specific Magnetic Resonance Imaging Contrast Agent Gd-EOB-DTPA

A convenient synthesis of disodium S-[4-(4-ethoxybenzyl)-3,6,9-tris[(carboxy-kappaO)methyl]-3,6,9-triazaundecandioato)(5-)-kappa(3)N(3)(),N(6)(),N(9)(),kappa(2)O(1)(),O(11)()]gadolinate(2-) (Gd-EOB-DTPA), 1, is reported. This water-soluble complex is presently undergoing phase III clinical trials as a liver-specific contrast agent for magnetic resonance imaging (MRI). The thermodynamic complex stability constant of 1 and the acid dissociation constants of the ligand have been determined as well as the stability constant of the calcium complex Ca-EOB-DTPA (2), which is used as an additive in the pharmaceutical formulation of the contrast agent. The solid-state structure of the ligand S-4-(4-ethoxybenzyl)-3,6,9-tris(carboxylatomethyl)-3,6,9-triazaundecanedioic acid (H(5)EOB-DTPA), 3, has been elucidated in a single crystal X-ray diffraction study. Additionally, HPLC evidence is given that the enantiomerically pure ligand forms two diastereomeric gadolinium complexes in a 65:35 ratio. The kinetics of isomerization of the isolated diastereomers-as dependent on pH and temperature-has been investigated, and thus, the activation energy for the interconversion of these isomers has been estimated to be 75.3 kJ mol(-1). Finally, the structures of the two components of 1 are discussed in terms of four possible diastereomers.

The podiatric examination

With the evolution of the AIDS epidemic into a relatively chronic disease, practitioners will continue to see an increase in the number of patients infected with HIV for the diagnosis and management of podiatric pathology. A thorough history and physical examination, taken with a complete knowledge base of HIV implications, will enhance the ability to form the strategies required to treat the manifestations of this disease and to request appropriate referrals. Laboratory studies and other diagnostic techniques have been developed and increased in specificity to allow for earlier and more precise identification of the presenting pathology. A continuously expanding choice of medications is available for treatment. The clinical presentations of HIV infection in the foot involve nearly all organ systems. This article reviews the podiatric role as part of the medical team in the diagnosis and treatment of patients infected with HIV.

Recurrent plantar ulceration following pan metatarsal head resection

Although the pan metatarsal head resection, since it was originally described and performed by Hoffman in 1911, has proven to be an effective and viable procedure in treating many forefoot deformities, it is not without its own complications. The authors provide an historical perspective of the pan metatarsal head resection, a discussion on the complication of recurrent plantar ulceration after the pan metatarsal head resection, and a review of their own experience with this procedure. A retrospective review was performed of all patients having undergone pan metatarsal resections between August 1980 and April 1993. Twenty procedures were performed on 12 patients with diabetic neuropathy, and 21 procedures were performed on 15 patients with rheumatoid arthritis. The incidence of recurrent plantar ulceration after surgical correction was 25% and 28%, respectively. All 27 patients underwent primary healing. The authors, therefore, conclude that the complication of recurrent plantar ulceration after this procedure is a very likely and distinct possibility.

Vascular hamartoma. A case report

A case of a vascular hamartoma occurring in the plantar aspect of the foot is reported. Surgical excision of the mass was the treatment of choice, and the surgery was performed after appropriate diagnostic measures had been undertaken. A normal postoperative course ensued, and no recurrence has been reported.

Footwear and ankle stability in the basketball player

Ankle stability in basketball players is affected by footwear. Athletic shoe manufacturers have introduced specialized lacing systems and high-top performance shoes to improve ankle stability. These performance shoes not only aid in preventing ankle injuries, but also protect injured ankles.