Baseline troponin-T is powerful predictor of mortality after coronary bifurcation stenting

Introduction

Considerable progress has been made in the treatment of coronary bifurcation stenosis. Anatomical characteristics of the lesion, however, fail to give information about the functional significance of the bifurcation stenosis. There is no study that systematically establishes the baseline functional significance of coronary stenosis and its effect on procedural and clinical outcomes.

Methods

Patients with significant angiographically bifurcation lesions defined as diameter stenosis >50% in main vessel and/or side branch were included. FFR was performed in main vessel (MV) and side branch (SB) before and after percutaneous coronary intervention (PCI). If FFR was ≤0.80 the lesion was considered functionally significant, and patients underwent PCI. For the group with FFR >0.80 – intervention was deferred. All patients were followed-up for vital status every 3 months. Cox regression analysis was performed to identify independent predictors of all-cause and cardiovascular death. The local ethics committee approved the study and patients signed informed consent for participation into registry.

Results

For mean follow-up of 38±18 months (median 40, IQR 23–55 months) all-cause mortality was numerically lower: 8.5% (n=7/82) in deferred group and 12.6% in stented group (n=11/76, p=0.387). The cardiac mortality was also numerically lower, but statistically not significant (9.8%, n=8/82 vs. 11.5%, n=10/88, p=0.714). On multivariate model, independent predictors were mitral regurgitation >1st degree – HR=1.778 (CI 1.100–2.874, p=0.019); dyslipidemia HR=0.765 (CI 0.594–0.985, p=0.038); hemoglobin concentration – HR=0.976 (CI 0.964–0.988, p<0.001); pre-PCI serum troponin ≥0.010 ng/ml – HR=2.702 (CI 1.451–5.032, p=0.002). On multivariate analysis, the following factors were identified as independent predictors of cardiac mortality: age – HR=1.035 (CI 1.009–1.062, p=0.009); diabetes – HR=1.789 (CI 1.089–2.962, p=0.024); dyslipidemia treated with statin – HR=0.667 (CI 0.515–0.863, p=0.002); LV posterior wall thickness – HR=1.230 (CI 1.062–1.424, p=0.006); mitral regurgitation more than 1st degree – HR=1.763 (CI 1.065–2.917, p=0.027); troponin pre-PCI ≥0.010 ng/ml – HR=2.498 (CI 1.228–5.081, p=0.011); true bifurcation lesion – HR=1.820 (CI 1.026–3.229, p=0.040); SBBARI score <10% – HR=1.715 (CI 1.049–2.804, p-0.031).

Conclusion

Baseline high-sensitive troponin T value is a strong predictor for both all cause and cardiac mortality in patients undergoing coronary bifurcation lesion PCI.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Alexandrovska University Hospital

Mid-term mortality after stenting of distal left main stenosis with regular, third generation drug eluting stent or dedicated bifurcation stent or surgery-registry based,all-comers data

Background

Distal left main (LM) bifurcation lesions remain a challenge for interventional cardiologists and they are associated with significant morbidity and mortality. The aim of the current study was to identify predictors of cardiac mortality at mid-term follow up after PCI (DES vs. dedicated bifurcation stent) or CABG.

Methods

All patients with distal LM stenosis ≥50% were included in prospective registry starting from 01.2015. The exclusion criteria for registry are cardiogenic shock, a priory life expectancy duration <1 year, lack of inform consent. All patients were prospectively followed about the alive status through the national security number data base. All deaths were deemed cardiac if proof otherwise (the data patient families or family's physicians were contacted through phone call about the reason of death)

Results

For three year follow up period (median 35 months, IQR 18–50) 303 patients were included. 220 patients were stented with 3rd generation DES, 43 with dedicated bifurcation stent BiOSS (Balton, Poland), and rest were sent for CABG. The mean age was 67±10 years, 72% were males, 37% diabetics, all with hypertension, 97% dyslipidemia, 15% PAD, 9% COPD, 16% carotid artery disease, previous MI 28%, previous PCI 50% - without significant difference between three groups. The frequency of acute coronary syndrome during admission was 11% - without difference in frequency between groups. The patient referred to CABG had significantly lower left ventricular EDV and ESV, more severe mitral regurgitation and kinetic disturbances, higher SYNTAX score and longer lesion length. On univariate COX regression analysis, the following factors were associated with mortality: age, NYHA class, GFR, baseline troponin, hemoglobin, LV EF, mitral regurgitation, kinetics disturbances, treatment with beta blockers, ACE inhibitors, statin, atrial fibrillation, SYNTAX score, lesion length. The type of treatment was not associated with differences in mortality (figure). On COX multiple regression survival analysis independent predictors of survival were: age (HR=1.036, CI 1.005–1.068, p=0.023); COPD (HR=2.313, CI 1.170–4.572, p=0.016); GFR (HR=0.988, CI 0.978–1.000, p=0.048); hemoglobin (HR=0.970, CI 0.955–0.986, p=0.000); left ventricular EF (HR=0.958, CI 0.832–0.985, p=0.003).

Conclusions

The type of treatment was not associated with mid-term mortality. Our data demonstrate that dedicated bifurcation stent could be used safely for distal LM stenosis treatment with similar safety as 3rd generation DES.

Funding Acknowledgement

Type of funding sources: None.

STRUCTURAL AND FUNCTIONAL VASCULAR CHANGES IN HIGH NORMAL ARTERIAL PRESSURE

The PURPUSE of the present study is changes in function and structure of large arteries in individuals with High Normal Arterial Pressure (HNAP) to be established. MATERIAL and METHODS: Structural and functional changes in the large arteries were investigated in 80 individuals with HNAP and in 45 with optimal arterial pressure (OAP). In terms of arterial stiffness, pulse wave velocity (PWV), augmentation index (AI), central aortic pressure (CAP), pulse pressure (PP) were followed up in HNAP group. Intima media thickness (IMT), flow-induced vasodilatation (FMD), ankle-brachial index (ABI) were also studied. RESULTS: Significantly increased values of pulse wave velocity, augmentation index, central aortic pressure, pulse pressure are reported in the HNAP group. In terms of IMT and ABI, being in the reference interval, there is no significant difference between HNAP and OAP groups. The calculated cardiovascular risk (CVR) in both groups is low. CONCLUSION: Significantly higher values of pulse wave velocity, augmentation index, central aortic pressure and pulse pressure in the HNAP group are reported.

P1963The determinants of functional significance of coronary bifurcation lesions and its implications on clinical follow up to 48 months (insights from FIESTA registry)

Background

There is no study up-to-now to determine the rate of functionally significant coronary bifurcation lesions, which have to be intervened and what are the clinical consequences of the FFR case selection strategy.

Methods

We analyzed patients from FIESTA registry, which was continuation of FIESTA study (Ffr vs. IcEcgSTA, ClinicalTrials.gov Identifier: NCT01724957). Patients with stable angina were included (if there were other coronary stenoses they were threated first after checking by FFR for functional significance). The inclusion criterions were angiographic bifurcation lesions in a native coronary artery with diameter ≥2.5 mm and ≤4.5 mm and SB diameter ≥2.0 mm. We excluded patients with ST-segment elevation myocardial infarction, left main, hemodynamic instability and those with non-cardiac co-morbidity conditions with a life expectancy of less than one year. PCI was performed according to the current guidelines. Provisional stenting was the default strategy in all patients. Two guidewires were inserted into both distal MB and SB. Initial FFR was performed using the PrimeWire or PrimeWire Prestige (Volcano Corp., USA). For all FFR measurements, intracoronary adenosine was given in increasing doses of 60 mcg, 120 mcg, and 240 mcg. The minimum value of FFR measurements was taken for analysis. All patients received double antiplatelet therapy with ADP-antagonist and aspirin for at least 12 months.

Results

A 130 consecutive patients with coronary bifurcation stenoses were included – 57 had positive FFR<.80 in main vessel of bifurcation lesion (44% functionally significant lesions). The mean age was 67±10 years, 66% males, 96% hypertensive, 39% diabetic, 96% dyslipidemic (or on treatment with statin), 55% smokers, 22% with previous myocardial infarction, 51% with previous PCI. The residual SYNTAX score before FFR bifurcation assessment was 13±4 (FFR<.80) vs. 8±3 (FFR≥0.80), p<0.001. Univariate predictors of bifurcation FFR<.80 were: proximal (MV%DS) or distal (MB%DS) main vessel stenosis ≥85% (derived from ROC analysis with overall accuracy 77% and 72%, accordingly), lesion length, SYNTAX score, triglyceride concentration, previous MI on lateral wall and carotid artery disease. On multivariate logistic analysis only MV%DS>85% (OR=8.929, CI 2.887–27.619, p<0.001), MB%DS>85% (OR=3.831, CI 1.349–10.883, p=0.012) and SYNTAX score≥12 (OR=16.466, CI 5.225–15.889, p<0.001). At median follow-up of 26 months (IQR 17–35) the all-cause mortality was 17.5% in FFR positive bifurcations vs. 4.1% in FFR negative lesions (log-rank =.067).

Conclusions

Less than a half of angiographically significant coronary bifurcation lesions are functionally significant and require stent implantation. The functional significance was related with higher degree stenosis in main vessel and overall disease severity estimated with SYNTAX score. A trend to lower mortality was noted in group with non-significant FFRs.

Photodynamic Action of Tri-meso (N-methylpyridyl), meso (N-tetradecyl-pyridyl) Porphine on Staphylococcus Epidermidis Biofilms Grown on Ti6Al4V Alloy

Staphylococcus epidermidis is a leading cause of nosocomial infections, and its virulence is attributable to formation of biofilm, especially on implanted devices. Photodynamic treatment (PDT) has been actively investigated for the eradication of bacterial biofilm growing on dental plaques and oral implants. In this study, we used Tri-meso (N-methyl-pyridyl), meso (N-tetradecyl-pyridyl) porphine (C14) for inactivation of two structurally distinct S. epidermidis biofilms grown on Ti6Al4V alloy and compared its photosensitizing efficiency with that of the parent molecule, tetra-substituted N-methylpyridyl-porphine (C1). A more significant reduction in bacterial survival was observed when both bacterial biofilms were exposed to a lower dose of C14, and simultaneously to visible light in comparison with C1. The different responses of both staphylococcal biofilms to C1- or C14-treatment appeared to depend on photosensitizer endocellular concentration. C14 bound to both biofilms to a greater extent than C1. Moreover, C14 penetrates deeper into the bacterial membranes, as determined by fluorescence quenching experiments with methylviologen, allowing for better bacterial killing photoefficiency. Confocal laser scanning microscope (CLSM) analysis indicated damage to bacterial cell membranes in both photodynamically treated biofilms, while disruption of PDT-treated biofilm was confirmed by scanning electron microscopy (SEM). In summary, C14 may be a potential photosensitizer for the inactivation of staphylococcal biofilms for many device-related infections which are accessible to visible light.

The 67P/Churyumov-Gerasimenko observation campaign in support of the Rosetta mission

We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively 'well-behaved' comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends-in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies.This article is part of the themed issue 'Cometary science after Rosetta'.

Expression of leptin, NGF and adiponectin in metabolic syndrome

Adipose tissue secretes a variety of adipokines involved in the regulation of energy metabolism and insulin resistance. Metabolic syndrome corresponds to a clinical condition in which white adipose tissue is characterized by an increased production and secretion of inflammatory molecules which may have local effects on adipose tissue physiology but also systemic effects on other organs. The aim of this study was to assess the expression of leptin, NGF and adiponectin in women with metabolic syndrome compared to healthy controls. Plasma leptin, NGF and adiponectin levels were measured by the ELISA method. Leptin and NGF immunohistochemical expression was analyzed in subcutaneous adipose tissue. The results indicated that in women with metabolic syndrome waist circumference, body mass index, HOMA index, glucose, total cholesterol and triglyceride levels were significantly increased in parallel with overxpressed plasma levels of leptin and NGF and decreased adiponectin. The immunohistochemical expression of leptin and NGF was very strong. In conclusion, this is the first study demonstrating a complex of immunochemical and immunohistochemical expression of the key adipokines including leptin, NGF and adiponectin in women with metabolic syndrome. Locally-produced pro-inflammatory adipokines probably contribute to the ethiopathogenic mechanisms ofmetabolic syndrome.

Fluorescence and Absorption Spectra of Phenylazopyrazolone Dyes

The absorption and fluorescence spectra of some arylazopyrazolone dyes have been investigated. The emission is assigned to their hydrazone form. A very good linear correlation is obtained between the σ Hammett constants and the differences of the absorption maxima of the hydrazone form and the anion. Quantum chemical calculations indicate to a charge migration upon exci­tation.

The electron donor substituents cause bathochromic and hypsochromic shifts in the absorption and in the fluorescence maxima resp., while the acceptor substituents shift bathochromically both maxima. All compounds studied except the p-N(CH3)2 derivative show an anomalously large Stokes shift in nonpolar solvents.

A New Class of Organic Luminophores With a Stilbene Chromophore: 3-Phenylmethylene-1(3H)-Isobenzofuranones

A new class of luminophores with a stilbene chromophore, 3-phenylmethylene-1(3H)-iso-benzofuranones (BPH's), has been investigated. The fluorescence occurs in the region 26000-16000 cm-1, the maximal quantum yield being about 0.6. As a result of substitution or higher polarity of the solvent the ππ* state of the BPH's separates from the fluorescently inactive nπ* state.

The S0-S2 absorption transition of the BPH's results from an excitation which is practically localized in the stilbene fragment. The good linear correlation of the fluorescence and absorption maxima and O-O transitions in ethanol with the σp-Hammett constants has been used for an interpretation of the changes in the potential hyperfaces of S0 and S1 states.

9-Aminofluorenium Cations: A New Group of anti-Aromatic Molecules

Quantum-chemical and spectral studies on the protonated form of fluorenone-anil show that this compound has anti-aromatic character. Its real structure should be considered as: 9-amino derivative of the anti-aromatic fluorenium cation.

Steady State and Dynamic Photophysical Properties of 2-Benzoimidazoleacetonitrile- α-Phenylmethylenes and 1-Aryl-2,2-Dicyanoethenes

The steady state and dynamic photophysical characteristics of newly synthesized 2-benzoimidazoleacetonitrile- α-phenylmethylenes (BIA’s) and 1-aryl-2,2-dicyanoethenes (DCE’s) have been investigated in solution at 300 K and in a frozen matrix at 77 K. The compounds have a very low or no emission in solution at 300 K both in non-polar and polar solvents. While in BIA’s a significant fluorescence ability is registered in a frozen ethanol matrix at 77 K, freezing solutions of DCE’s at 77 K does not lead to the appearance of either fluorescence or phosphorescence at 77 K even in the presence of C2H5J. The comparison of the fluorescence ability in aprotic and protic solvents does not show any evidence for the specific influence of the protondonating ability of the solvents on the weak fluorescence caused by the formation of intramolecular hydrogen bonds in excited states. The high fluorescence quantum yield of BIA’s in a frozen matrix at 77 K indicates that intramolecular libration of two heavy groups in the allyl chain is the reason for the weak fluorescence at 300 K. Quantum-chemical calculations support the hypothesis of quenching processes in the excited state of BIA’s at 300 K.

Regulation of the inner membrane mitochondrial permeability transition by the outer membrane translocator protein (peripheral benzodiazepine receptor)

We studied the properties of the permeability transition pore (PTP) in rat liver mitochondria and in mitoplasts retaining inner membrane ultrastructure and energy-linked functions. Like mitochondria, mitoplasts readily underwent a permeability transition following Ca(2+) uptake in a process that maintained sensitivity to cyclosporin A. On the other hand, major differences between mitochondria and mitoplasts emerged in PTP regulation by ligands of the outer membrane translocator protein of 18 kDa, TSPO, formerly known as the peripheral benzodiazepine receptor. Indeed, (i) in mitoplasts, the PTP could not be activated by photo-oxidation after treatment with dicarboxylic porphyrins endowed with protoporphyrin IX configuration, which bind TSPO in intact mitochondria; and (ii) mitoplasts became resistant to the PTP-inducing effects of N,N-dihexyl-2-(4-fluorophenyl)indole-3-acetamide and of other selective ligands of TSPO. Thus, the permeability transition is an inner membrane event that is regulated by the outer membrane through specific interactions with TSPO.

Inclusion of 5-[4-(1-dodecanoylpyridinium)]-10,15,20-triphenylporphine in supramolecular aggregates of cationic amphiphilic cyclodextrins: physicochemical characterization of the complexes and strengthening of the antimicrobial photosensitizing activity

Recent findings suggest that visible light-promoted photooxidative processes mediated by sensitizers of appropriate chemical structure could represent a useful tool for properly addressing the problem of the increasing occurrence of infectious diseases caused by multiantibiotic-resistant microbial pathogens. The monocationic meso-substituted porphyrin 5-[4-(1-dodecanoylpyridinium)]-10,15,20-triphenyl-porphine (TDPyP) complexed into supramolecular aggregates of cationic amphiphilic beta-cyclodextrin (SC(6)NH(2)) (mean diameter = 20 nm) appeared to be endowed with favorable properties to act as a photosensitizing agent, including a very high quantum yield (Phi(Delta) = 0.90) for the generation of the highly reactive oxygen species, singlet oxygen ((1)O(2)). Although the yield of (1)O(2) generation was comparable to that obtained after TDPyP incorporation into cationic unilamellar liposomes of N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTAP) SC(6)NH(2)-bound TDPyP was more active than DOTAP-bound TDPyP in photosensitizing the inactivation of the Gram-positive methicillin-resistant bacterium Staphylococcus aureus (MRSA). At variance with DOTAP-bound TDPyP, photoactivated SC(6)NH(2)-bound TDPyP was efficient also in photokilling Gram-negative bacterial pathogens, such as Escherichia coli . These observations are in agreement with the well-known photobactericidal effect of positively charged porphyrin derivatives, which can be markedly enhanced after incorporation into carriers with multiple positive charges. In addition, transmission electron microscopy studies revealed that potentiation of the TDPyP-mediated photobactericidal effect by incorporation into SC(6)NH(2) is a consequence of the carrier's ability to promote an efficient crossing of the very tightly organized three-dimensional architecture of the bacterial outer wall by the embedded porphyrin so that a prompt interaction between the short-lived photogenerated (1)O(2) and the nearby targets, whose integrity is critical for cell survival, can take place.

Early Excited State Dynamics of 6-Styryl-Substituted Pyrylium Salts Exhibiting Dual Fluorescence

A series of 6-styryl-2,4-diphenylpyrylium salts exhibiting dual fluorescence has been investigated by fluorescence up-conversion in conjunction with quantum chemical calculations. The short-wavelength emission is due to an excited state localized on the pyrylium fragment and the long-wavelength emission arises from a charge-transfer state delocalized over the whole molecule. The two fluorescing states do not exhibit a precursor-successor relationship. The rise time of the short-wavelength fluorescence is smaller than 200 fs, and that of the long-wavelength emission depends on the electron-donating property of the styryl group substituent. The rise is almost prompt with the weaker donors but is slower, wavelength and viscosity dependent with the strongest electron-donating group. A model involving a S(2)/S(1) conical intersection is proposed to account for these observations.

Fluorescence properties and conformational stability of the β-hemocyanin of Helix pomatia

The beta-hemocyanin (beta-HpH) is one of the three dioxygen-binding proteins found freely dissolved in the hemolymph of the gastropodan mollusc Helix pomatia. The didecameric molecule (molecular mass 9 MDa) is built up of only one type of subunits. The fluorescence properties of the oxygenated and apo-form (copper-deprived) of the didecamer and its subunits were characterized. Upon excitation of the hemocyanins at 295 or 280 nm, tryptophyl residues buried in the hydrophobic interior of the protein determine the fluorescence emission. This is confirmed by quenching experiments with acrylamide, cesium chloride and potassium iodide. The copper-dioxygen system at the binuclear active site quenches the tryptophan emission of the oxy-beta-HpH. The removal of this system increases the fluorescence quantum yield and causes structural rearrangement of the microenvironment of the emitting tryptophyl residues in the apo-form. Time-resolved fluorescence measurements show that the oxygenated and copper-deprived forms of the beta-HpH and its subunits exist in different conformations. The thermal stability of the oxy- and apo-beta-HpH is characterized by a transition temperature (Tm) of 84 degrees C and 63 degrees C, respectively, obtained by differential scanning calorimetry. Increase of the temperature influences the active site at lower temperatures than the environments of tryptophans and tyrosines causing a loss of oxygen bound to the copper atoms. This process is, at least partially, reversible as after cooling of the protein samples, around 60% reinstatement of the copper-peroxide band has been observed. The results confirm the role of the copper-dioxygen complex for the stabilization of the hemocyanin structure in solution. The other important stabilizing factor is oligomerization of the hemocyanin molecule.

Adsorption of NO on alumina-supported oxides and oxide–hydroxides of manganese

The adsorption capacity for NO of alumina-supported oxides and oxide-hydroxides of manganese have been studied. Two series of samples have been prepared by precipitation on gamma-alumina and appropriate thermal treatment. The samples have been characterized by adsorption methods, magnetic methods, electronic paramagnetic resonance (EPR), transient response technique, and temperature-programmed desorption (TPD). The influence of the concentration of the initial manganese-containing solution has been investigated. The sample, prepared with a solution with Mn concentration of 4 g/100 ml, has been shown to be the best adsorbent for NO under the conditions of the experiment. It has been found that the presence mainly of Mn3+ ions on the surface of the support is probably responsible for the enhanced adsorption capacity.

Discrimination between two steps in the mitochondrial permeability transition process

It is well known that a lag phase generally elapses between the addition of inducers of the mitochondrial permeability transition and the opening of the pore. To advance our present understanding as regards the significance of this phenomenon, we used experimental approaches which are sensitive to different aspects of the permeability transition process. The pore conformation was sensed by the fluorescence anisotropy changes of hematoporphyrin-labelled mitochondria. Membrane permeabilization was ascertained by following the matrix swelling consequent to external solute equilibration. We show that the anisotropy changes of mitochondria-bound hematoporphyrin precede both membrane depolarization (proton permeation) and matrix swelling (solute permeation), thus sensing a step of the permeability transition process that involves the pore in its closed state. We suggest that the opening of the pore is preceded by a structural remodelling of mitochondrial domains containing hematoporphyrin-near, pore-regulating histidines. Such a perturbation is strongly inhibited at acidic matrix pH and completely blocked by cyclosporin A. In sucrose-based media the opening of the pore can be strongly delayed, as compared to salt-based media, a fact which probably reflects perturbation of mitochondrial membranes by sugar. We conclude that the mitochondrial permeability transition could be described as an at least two-step process which is mainly regulated by conformational changes of the pore components.

Structure and stability of arthropodan hemocyanin Limulus polyphemus

In the hemolymph of many arthropodan species, respiratory copper proteins of high molecular weight, termed hemocyanins (Hcs) are dissolved. In this communication, we report on the protein stability of different hemocyanin species (Crustacea and Chelicerata) using fluorescence spectroscopy. Five to seven major electrophoretically separable protein chains (structural subunits) were purified by fast protein liquid chromatography (FPLC) ion exchange chromatography from different hemocyanins with very high sequence homology of the active site regions binding copper ions (CuA and CuB), and especially the relative sequence positions of histidine (His) and tryptophan (Trp) residues of these protein segments are in all cases identical. The conformational stabilities of the native dodecameric aggregates and their isolated structural subunits towards various denaturants (pH and guanidine hydrochloride (Gdn.HCl)) indicate that the quaternary structure is stabilized by hydrophilic and polar forces, whereby both, the oxy- and apo-forms of the protein are considered. These two classes of Crustacea and Chelicerata Hcs have the similar Trp-fluorescence quantum yields, but different values of lambda(max) emission (about 325 and 337 nm, respectively). Differences in the quantum yields are observed of the oxy- and apo-forms, which must be attributed to the fluorescence quenching effect of the two copper ions (CuA and CuB) in the active site. The position of emission maximum indicates tryptophan side chains are situated in a non-polar environment. Denaturation studies of Hcs by Gdn.HCl indicate that the denaturation process consists of two steps: dissociation of the native molecule into its structural subunits and denaturation of the subunits at concentrations >1.5M Gdn.HCl. Two steps of denaturation are also observed after keeping the protein in buffer solutions at different pH values with different pH-stability for holo-oxy and apo-Hc forms.

Meso-substituted tetra-cationic porphyrins photosensitize the death of human fibrosarcoma cells via lysosomal targeting

In this paper we present a study on the intracellular localisation and the efficiency of cell photoinactivation of a series of derivatives of 5,10,15,20-tetrakis-(4-N-methylpyridyl)-porphine (C1), whose degree of lipophilicity was varied through replacement of one methyl group with an alkyl chain of various length. Human HT1080 fibrosarcoma cells exposed to the various C1 derivatives (0.25 microM) for 24 h and irradiated with increasing doses of red-light (0.45-27 J/cm2) were inactivated with different efficiencies. The efficiency of cell photoinactivation increased with the increasing length of the hydrocarbon tail and lipophilicity and correlated with the efficiency of the porphyrin accumulation into the cells. Despite the presence of positive charges, these porphyrins did localise rather selectively in lysosomes while mitochondrial localisation was not evident, as demonstrated by fluorescence microscopy studies. Studies on isolated mitochondria provided evidence that the porphyrin uptake and distribution in these organelles were not modulated by the transmembrane potential but were exclusively controlled by partitioning phenomena which might have prevented mitochondria localization in whole cells. Our findings demonstrated that these porphyrins entered the cells through the endocytotic pathway and were transported to lysosomes whose pH increased rapidly upon irradiation. Lysosomal damage did not cause any intracellular redistribution of the porphyrin and represented the primary event causing cell death, very likely via necrosis.

Conformational states of the Rapana thomasiana hemocyanin and its substructures studied by dynamic light scattering and time-resolved fluorescence spectroscopy

Hemocyanins are dioxygen-transporting proteins freely dissolved in the hemolymph of mollusks and arthropods. Dynamic light scattering and time-resolved fluorescence measurements show that the oxygenated and apo-forms of the Rapana thomasiana hemocyanin, its structural subunits RtH1 and RtH2, and those of the functional unit RtH2e, exist in different conformations. The oxygenated respiratory proteins are less compact and more asymmetric than the respective apo-forms. Different conformational states were also observed for the R. thomasiana hemocyanin in the absence and presence of an allosteric regulator. The results are in agreement with a molecular mechanism for cooperative dioxygen binding in molluscan hemocyanins including transfer of conformational changes from one functional unit to another.

Fluorescence studies on denaturation and stability of recombinant human interferon-gamma

Unfolding/folding transitions of recombinant human interferon-gamma (hIFNgamma) in urea and guanidine chloride (Gn.HCl) solutions were studied by fluorescence spectroscopy. At pH 7.4 Gn.HCl was a much more efficient denaturant (midpoint of unfolding C* = 1.1 M and deltaG0 = 13.4 kJ/mol) than urea (C* = 2.8 M and deltaG0 = 11.7 kJ/mol). The close deltaG0 values indicate that the contribution of electrostatic interactions to the stability of hIFNgamma is insignificant. Both the pH dependence of the fluorescence intensity and the unfolding experiments in urea at variable pH showed that hIFNgamma remains native in the pH range of 4.8-9.5. Using two quenchers, iodide and acrylamide, and applying the Stern-Volmer equation, a cluster of acidic groups situated in close proximity to the single tryptophan residue was identified. Based on the denaturation experiments at different pH values and on our earlier calculations of the electrostatic interactions in hIFNgamma, we assume that the protonation of Asp63 causes conformational changes having a substantial impact on the stability of hIFNgamma.

Structure-function relationships in the neurotoxin Vipoxin from the venom of Vipera ammodytes meridionalis

The neurotoxic complex Vipoxin is the lethal component of the venom of Vipera ammodytes meridionalis, the most toxic snake in Europe. It is a complex between a toxic phospholipase A2 (PLA2) and a non-toxic and catalytically inactive protein, stabilizing the enzyme and reducing the activity and toxicity. Structure-function relationships in this complex were studied by spectroscopic methods. A good correlation between the ionization behaviour and accessible surface area (ASA) of the tyrosyl residues was observed. In the toxic PLA2 subunit phenolic groups participate in H-bonding network that stabilizes the catalytically and pharmacologically active conformation. The tryptophan fluorescence decay of Vipoxin is well fitted by two exponentials with lifetimes of 0.1 (54%) and 2.5 (46%) ns. W20P, W31P and W31I are located in the interface between the two subunits and participate in hydrophobic interactions stabilizing the complex. Dissociation of the complex leads to a transition of the tryptophans from hydrophobic to hydrophilic environment, which influences mainly tau2. The longer lifetime is more sensitive to the polarity of the environment. Circular dichroism measurements demonstrate that the two components of the neurotoxin preserve their secondary structure after dissociation of the complex. The results of the spectroscopic studies are in accordance with a mechanism of blockade of transmission across the neuromuscular junctions of the breathing muscles by interaction of a dissociated toxic PLA2 with a membrane. The loss of toxicity is connected with slight changes in the secondary structure of PLA2. CD studies also show a substantial contribution of disulfide bonds to the stability of the neurotoxic complex and its components.

Fluorescence spectroscopy of the tryptophan microenvironment in Carcinus aestuarii hemocyanin

The steady-state and time-resolved fluorescence properties of the multitryptophan minimal subunit CaeSS2 from Carcinus aestuarii hemocyanin have been studied with the aim of probing the environment of the fluorophores within the protein matrix. Subunit a of Panulirus interruptus hemocyanin, whose X-ray structure is known, has been also studied. The results are compared with those collected with other two monomeric fractions (CaeSS1, CaeSS3) produced by dissociation of the native, oligomeric protein as well as with those of the hexameric aggregate. Three classes of tryptophan residues can be singled out by a combination of fluorescence quenching and lifetime measurements on the holo-Hc (the copper containing, oxygen binding form) and the apo-Hc (the copper-free derivative). One class of tryptophans is exposed to the protein surface. Some of these residues are proposed to be involved in the intersubunit interactions in CaeSS1 and CaeSS3 fractions whereas in CaeSS2 the protein matrix masks them. This suggests the occurrence of conformational rearrangements after detachment of the subunit from the native aggregate, which could explain the inability of CaeSS2 to reassociate. A second class of tryptophan has been correlatively assigned, by comparison with the results obtained with Panulirus interruptus hemocyanin, to residues in close proximity to the active site. The third class includes buried, active site-distant, residues.

Luminescence Properties of Some Coumarins with 3:4-Fused Ring System

The photophysical characteristics of a group of coumarins with a 3:4-fused ring system (2-substitut-ed-4,5-dioxo-l,2-dihydro-4H,5H-pyrano-[3:4-c] [1]-benzopyrans) in solutions at room temperature, in frozen ethanol matrix at 77 K, in solid phase and in PVC films are reported. The low fluorescence quan-tum yield of the compounds investigated in solution is explained as a result of internal conversion from the fluorescent S2 (ππ*) state to the lower lying S1(nπ*) state. The phosphorescence with a life time in the order of seconds is connected with intersystem crossing S1 (nπ*) -T1(ππ*). The absorption Franck Condon transitions in solid phase and in PVC matrix are only weekly batochromically shifted accord-ing to solution.

Steady-state and time-resolved fluorescence of Esperase: comparison with the X-ray structure in the region of the two tryptophans

Fluorescence emission properties of the alkaline protease Esperase have been investigated using steady-state and time-resolved fluorescence spectroscopy. The local polarity and solvent accessibility of the tryptophyl chromophores is characterized. Quenching studies demonstrated that Trp 6 and Trp 113 are 'buried' to acrylamide, iodide ions and caesium ions. An abnormally low tryptophan quantum yield was calculated showing that the emission of the two indole rings is significantly quenched by nearby side chains or peptide bonds. The fluorescence decay of PMS-Esperase was well fitted by two exponentials with lifetimes of 2.7 and 0.35 ns. X-ray data for Esperase (S. Klupsch, Ph.D. Thesis, University of Hamburg, Hamburg, Germany) in the region of the two tryptophans were used to explain the observed emission properties. Gln 182 and Asn 204 as well as Asn 117 and Met 119 are the most likely quenchers, respectively, of the Trp 6 and Trp 113 fluorescence. The two tryptophans in Esperase are 'buried' in hydrophobic regions and are excellent intrinsic probes to study folding-unfolding reactions. Experiments in the presence and absence of added calcium ions demonstrated the stabilizing role of the Ca(2+)-binding sites.

Fluorescence decay of tryptophans in serine proteinases from microorganisms: relation to X-ray models

Fluorescence decay kinetics of indole groups in five proteinases from microorganisms are reported. The data show differences between the excited state lifetimes of the tryptophans located in identical positions in the polypeptide chains of the closely related proteinases mesentericopeptidase and subtilisin Novo. The lifetime of the single Trp 113 in subtilisins DY and Carlsberg are identical. The microenvironments of this residue in the four subtilisins are identical and probably its fluorescence is quenched in these proteins. The crystallographic models of the enzymes investigated were analysed in the region of the tryptophyl residues and provide an explanation for the observed emission properties.

Interaction of phthalocyanines with lipid membranes: a spectroscopic and functional study on isolated rat liver mitochondria

Absorption and emission spectroscopic studies on Zn(II)-phthalocyanine (ZnPc) incorporated into unilamellar liposomes of dipalmitoylphosphatidylcholine, sometimes added with cholesterol or cardiolipin, and released to rat liver mitochondria via the three types of liposomal vesicles indicated that: (a) ZnPc predominantly dissolves in all lipid domains of biological membranes with the exception of cardiolipin-containing regions; a partial localization of ZnPc in protein binding sites is also postulated; (b) the spectroscopic properties of ZnPc, although mainly determined by the aggregation state of the dye, are somewhat influenced by the physico-chemical characteristics of the lipid environment; (c) ZnPc-binding lipid domains in mitochondria are mainly localized in the outer membrane; this conclusion is clearly deduced from the trends of Arrhenius plots of the ZnPc fluorescence quantum yield in whole mitochondria and isolated inner or outer membrane in the temperature range -10 degrees C-(+)45 degrees C; (d) the nature of the ZnPc-binding site in mitochondria is not dependent on the chemical composition of the liposome carrier, contrary to what observed for other hydrophobic dyes, such as porphyrins. This has been also confirmed by photosensitization experiments. Actually, illumination of ZnPc-loaded mitochondria by 600-700 nm light causes a decline of the respiratory control ratio, which is essentially dependent on the amount of incorporated photosensitizer, irrespective of the composition of the carrier.

Luminescence Properties and Electronic Structure of Some Quinolizinone and Indolizinone Derivatives

The absorption and luminescence static and dynamic properties of a group of quinolizinone and indolizinone derivatives in solvents of different polarity at 297 K and 77 K are studied. On the basis of the spectral data and the PPP quantum-chemical results the problem of the main chromophore in these structures is discussed

[Radionuclear encephalo-angioscintigraphic studies in transitory disorders of brain circulation in childhood]

Fifteen cases of transient cerebral ischaemia in children have been studied. Radionuclear encephaloangioscintigraphy (RNEAS) with Tc99 DTPA in combination with CT scanning, doppler sonography of extracranial head arteries and EEG were performed in all observed cases. For some children cerebral angiography was done. RNEAS study found out: stenosis of internal carotid artery or a. cerebri media in 5 cases; AV-malformations- 3; ischaemic area- 1, aneurysma- 1; increased blood permeability of the late static scintigraphy- 3. Positive correlation was established between the angioscintigraphic and sonographic findings in the cases with stenosis of internal carotid artery; between angioscintigraphic and CT results in the cases with ischaemia; between RNEAS and angiographic data in cases with AV-malformations, aneurysm and stenosis. In conclusion RNEAS could be considered as a useful, atraumatic screening method within the complex of laboratory examinations for vascular diseases in childhood.

Synthesis, Structure and Spectral Properties of Pyrylium Salts and Their Derivatives. I. 5,6-Dihydro-benzo(c)xanthylium Salts

The synthesis and spectral properties of a group of xanthylium salts are described. The longest wavelength absorption maximum in organic solvents (ethanol, 1,4-dioxane, acetonitrile) is the region 17 000-20 000 cm-1, the molar absorptivity exceeding 30 000 1 • mol-1 cm-1. The fluorescence Frank Condon transition is in the region 16 000-19 000 cm-1, the fluorescence quantum yield of some of the compounds is greater than 0.9. The relation between the structure and the spectral properties of the molecules is interpreted by means of PPP-quantumchemical calculations.