The pursuit of stability in halide perovskites: the monovalent cation and the key for surface and bulk self-healing.

We find significant differences between degradation and healing at the surface or in the bulk for each of the different APbBr3 single crystals (A = CH3NH3+, methylammonium (MA); HC(NH2)2+, formamidinium (FA); and cesium, Cs+). Using 1- and 2-photon microscopy and photobleaching we conclude that kinetics dominate the surface and thermodynamics the bulk stability. Fluorescence-lifetime imaging microscopy, as well as results from several other methods, relate the (damaged) state of the halide perovskite (HaP) after photobleaching to its modified optical and electronic properties. The A cation type strongly influences both the kinetics and the thermodynamics of recovery and degradation: FA heals best the bulk material with faster self-healing; Cs+ protects the surface best, being the least volatile of the A cations and possibly through O-passivation; MA passivates defects via methylamine from photo-dissociation, which binds to Pb2+. DFT simulations provide insight into the passivating role of MA, and also indicate the importance of the Br3- defect as well as predicts its stability. The occurrence and rate of self-healing are suggested to explain the low effective defect density in the HaPs and through this, their excellent performance. These results rationalize the use of mixed A-cation materials for optimizing both solar cell stability and overall performance of HaP-based devices, and provide a basis for designing new HaP variants.

CD84 mediates CLL-microenvironment interactions.

Chronic lymphocytic leukemia (CLL) is a malignant disease of small mature lymphocytes. Signals from the CLL microenvironment promote progression of the disease and induce drug resistance. This phenomenon is largely dependent on direct contact between the malignant B cells and stromal cells. CD84 belongs to the signaling lymphocyte activation molecule family of immunoreceptors, which self-associates, forming an orthogonal homophilic dimer. We therefore hypothesized that CD84 may bridge between CLL cells and their microenvironment, promoting cell survival. Our in vitro results show that CD84 expressed on CLL cells interact with CD84 expressed on cells in their microenvironment, inducing cell survival in both sides. Blocking CD84 in vitro and in vivo disrupt the interaction of CLL cells with their microenvironment, resulting in induced cell death. Thus, our findings suggest novel therapeutic strategies based on the blockade of this CD84-dependent survival pathway.

Development of Conductometric Sensor Based on 25,27-Di-(5-thio-octyloxy)calix[4]arene-crown-6 for Determination of Ammonium.

The conductometric sensor based on 25,27-di-(5-thio-octyloxy)calix[4]arene-crown-6 was developed for the quantitative analysis of ammonium. The calixarene was immobilized on the surface of the planar interdigitated electrodes by attachment of its dialkyl sulfide groups to the surface of the gold electrodes. The intrinsic ability of the calixarene to capture ammonium was studied in the conductometric measuring mode and by the electrochemical impedance spectroscopy. The developed sensor showed high selectivity to ammonium in the presence of mono-, di-, and trivalent cations. Selective and highly sensitive detection of ammonium resulted from the complexation between the ammonium ions and a crown-ether fragment of the upper rim of the 25,27-di-(5-thio-octyloxy)calix[4]arene-crown-6 macrocycle. The developed sensor had high signal repeatability. Its sensitivity was found to be satisfactory for the forthcoming sensor application in the water-sample analysis; the linear range was 0.01-1.5 mM and limit of detection 10 µM.

CALIX[4]ARENES AS MODULATORS OF ENERGY-DEPENDENT CA2+_ACCUMULATION AND FUNCTIONING OF THE ELECTRON TRANSPORT CHAIN IN SMOOTH MUSCLE MITOCHONDRIA.

The influence of supramolecular macrocyclic compounds calix[4]arenes (C-97, C-99, C-107) at a concentration of 100 nM in the process of energy-dependent Ca²âº-transport in isolated mitochondria of smooth muscle, as well as autofluorescence mitochondrial coenzyme NADH, FAD and hydrodynamic diameter of these organelles was investigated. Using Ca²âº-sensitive fluorescent dye Fluo-4 AM it was shown that the selected calix[4]arenes can suppress energy-dependent accumulation of Ca²âº by mitochondria. Accumulation of Ca²âº (80 jiM in the medium) accompanied by the growth of the fluorescent probe response from a conventional unit to a value of 1,57±0,04 (n=5). Calix[4]arenes C-97, C-99, C-107 falls fluorescent signal below the 0,88±0,08, 0,92±0,08 and 0,78±0,04 respectively. Thus, the selected calix[4]arenas lead to release of previously accumulated Ca2+ from mitochondria. Under the influence of C-97 and C-99 fluorescent signal from NADH reduced to -0,11±0,02 and -0,12±0,02, respectively, in relation to the reference value - -0,05±0,01 (n=5). Analysis of fluorescence response NADH and FAD in a suspension of isolated mitochondria suggests that the effects of test compounds on the functional activity of the electron transport chain is associated with the initial stimulation of its 1-th complex and subsequent inhibition of Ca²âº-dependent NAD- containing Krebs cycle dehydrogenases. Along with this, the use of photon correlation spectroscopy to assess changes in the volume of mitochondria (their hydrodynamic diameter) under the action of selected calix[4]arenes has shown that interference with the electron transport chain leads to changes in the osmotic balance between the matrix of the mitochondria and the external environment. The result is the growth of isolated organelles volume. In particular, the hydrodynamic diameter of mitochondria increased by 22±6 % and 34±8 % (n=5) in presence of C-97 or C-99. The conclusion was done about the advisability of further studies of the calyx[4]arenes effect on smooth muscle Ca²âº-homeostase and mitochondrial bioenergetics in order to find effective modifiers of their func- tional activity.

Calix[4]arene C-90 and its analogs activate ATPase of the myometrium myosin subfragment-1.

Numerous female reproductive abnormalities are consequences of disorders in uterus smooth muscle (myometrium) contractile function. In this work, we described activators of ATPase, which could be used for development of effective treatments for correcting this dysfunction. Myosin ATPase localized in the catalytic domain of myosin subfragment-1 transforms a chemical energy deposited in macroergic bonds of ATP into mechanical movement. It was shown that сalix[4]arene C-90 and its structural analogs functionalized at the upper rim of macrocycle with four or at least two N-phenylsulfonуltrifluoroacetamidine groups, are able to activate ATP hydrolysis catalyzed by myometrium myosin subfragment-1. It was shown with the method of computer modeling that N-phenylsulfonуltrifluoroacetamidine groups of calix[4]arene C-90 interact with responsible for binding, coordination and the hydrolysis of ATP amino acid residues of myosin subfragment-1. The results can be used for further research aimed at using calix[4]arene C-90 and its analogs as pharmacological compounds that can effectively normalize myometrium contractile hypofunction.

FURIN INHIBITORS BASED ON THE DERIVATIVES OF CALIX[4]ARENE CX3im.

The aim of this work was to study antifurin activity of some derivatives of calix[4]arenes modified on the upper rim of the macrocycle by positively charged or uncharged groups. It was found that calixarene CX3im derivatives containing positively charged N-methylimidazolium cycles were indeed able to inhibit furin (K(i) = 58.2 µM). The magnitude of the effects depended also on the hydrophobicity of the substituents located on the lower rim of the macrocycle. The findings indicated the possibility of creating furin inhibitors of new generation based on the calix[4]arene platform.

CALIX[4]ARENE C-99 INHIBITS MYOSIN ATPase ACTIVITY AND CHANGES THE ORGANIZATION OF CONTRACTILE FILAMENTS OF MYOMETRIUM.

Calix[4]arenes are cup-like macrocyclic (polyphenolic) compounds, they are regarded as promising molecular "platforms" for the design of new physiologically active compounds. We have earlier found that calix[4]arene C-99 inhibits the ATPase activity of actomyosin and myosin subfragment-1 of pig uterus in vitro. The aim of this study was to investigate the interaction of calix[4]arene C-99 with myosin from rat uterine myocytes. It was found that the ATPase activity of myosin prepared from pre-incubated with 100 mM of calix[4]arene C-99 myocytes was almost 50% lower than in control. Additionally, we have revealed the effect of calix[4]arene C-99 on the subcellular distribution of actin and myosin in uterus myocytes by the method of confocal microscopy. This effect can be caused by reorganization of the structure of the contractile smooth muscle cell proteins due to their interaction with calix[4]arene. The obtained results demonstrate the ability of calix[4]arene C-99 to penetrate into the uterus muscle cells and affect not only the myosin ATPase activity, but also the structure of the actin and myosin filaments in the myometrial cells. Demonstrated ability of calix[4]arene C-99 can be used for development of new pharmacological agents for efficient normalization of myometrial contractile hyperfunction.

Calix[4]arene C-90 selectively inhibits Ca2+,Mg2+-ATPase of myometrium cell plasma membrane.

The supramolecular compound calix[4]arene C-90 (5,11,17,23-tetra(trifluoro)methyl(phenylsulfonylimino)-methylamino-25,26,27,28-tetrapropoxycalix[4]arene) is shown to efficiently inhibit the ATP hydrolase activity of Ca2+,Mg2+-ATPase in the myometrium cell plasma membrane fraction and also in a preparation of the purified enzyme solubilized from this subcellular fraction. The inhibition coefficient I0.5 values were 20.2 ± 0.5 and 58.5 ± 6.4 µM for the membrane fraction and the solubilized enzyme, respectively. The inhibitory effect of calix[4]arene C-90 was selective comparatively to other ATPases localized in the plasma membrane: calix[4]arene C-90 did not influence the activities of Na+,K+-ATPase and "basal" Mg2+-ATPase. The inhibitory effect of calix[4]arene C-90 on the Ca2+,Mg2+-ATPase activity was associated with the cooperative action of four trifluoromethylphenylsulfonylimine (sulfonylamidine) groups oriented similarly on the upper rim of the calix[4]arene macrocycle (the calix[4]arene "bowl"). The experimental findings seem to be of importance for studies, using calix[4]arene C-90, of membrane mechanisms of regulation of calcium homeostasis in smooth muscle cells and also for investigation of the participation of the plasma membrane Ca2+-pump in control of electro- and pharmacomechanical coupling in myocytes.

In vivo dynamic light scattering microscopy of tumour blood vessels.

We present a study investigating the use of dynamic light scattering microscopy based on the temporal laser speckle's contrast that is produced over time by red blood cells (RBCs) flowing inside tumour blood vessels. The proposed noninvasive methodology is capable of producing high-resolution images of tumour vasculature. The technique is effective at producing images from tissue at a significant depth, as well as potentially having the ability to monitor tumour perfusion. An advantage of this methodology is that it has improved depth penetration compared with conventional imaging techniques (such as reflected-light microscopy), and one can avoid the use of any fluorescent or artificial chemicals for labeling. This is advantageous since labeling materials can affect imaging and animal welfare with respect to experiments that require continuous and repetitive monitoring.

Optical resolution of phosphorus containing calix[4]arenes by additive RP HPLC method.

The RP HPLC method (LiChrosorb RP18 or Separon SGX C18 column, acetonitrile-water 86:14 v/v mobile phase) was applied for enantiomeric separation of topologically chiral 5-bromo-25,26-bis(diethoxyphosphoryl)calix[4]arene 9 or 25-ethyl-26-dihydroxyphosphoryl-calix[4]arene 5. Separation of calixarene 9 was achieved by the addition of D-(-)-tartaric acid which formed hydrogen bonded diastereomeric associates with 9 to the mobile phase. Calixarenephosphoric acid 5 was transformed into diastereomeric salt 6 by addition of L-(-)-alpha-phenylethylamine before RP HPLC separation.