Visual sensing of fluoride ions by dipyrrolyl derivatives bearing electron-withdrawing groups

Two new, easy-to-prepare dipyrrolyl derivatives endowed with electron-withdrawing quinone or dicyano functionalities in their architecture permit the detection of fluoride ions under visual (naked-eye) as well as optical (absorption and fluorescence) and electrochemical conditions in organic solvents

New mixed ligand complexes of ruthenium(II) that incorporate a modified phenanthroline ligand: synthesis, spectral characterization and DNA binding

The hexafluorophosphate and chloride salts of two ruthenium(II) complexes, viz. [Ru(phen)(ptzo)2]2 and [Ru(ptzo)3]2+, where ptzo = 1,10-phenanthrolino[5,6-e]1,2,4-triazine-3-one (ptzo) - a new modified phenanthroline (phen) ligand, have been synthesised. These complexes have been characterised by infrared, UV-Vis, steady-state emission and1H NMR spectroscopic methods. Results of absorption and fluorescence titration as well as thermal denaturation studies reveal that both thebis- and tris-complexes of ptzo show moderately strong affinity for binding with calf thymus (CT) DNA with the binding constants being close to 105M-1 in each case. An intercalative mode of DNA binding has been suggested for both the complexes. Emission studies carried out in non-aqueous solvents and in aqueous media without DNA reveal that both [Ru(phen)(ptzo)2]2+ and [Ru(ptzo)3]2+ are weakly luminescent under these solution conditions. Successive addition of CT DNA to buffered aqueous solutions containing [Ru(phen)(ptzo)2]2+results in an enhancement of the emission. These results have been discussed in the light of the dependence of the structure-specific deactivation processes of the MLCT state of the metallo-intercalator with the characteristic features of its DNA interaction. In doing so, attempts have been made to compare and contrast its properties with those of the analogous phenanthroline-based complexes including the ones reported by us previously

A new family of donor-acceptor systems comprising tin(IV) porphyrin and anthracene subunits: synthesis, spectroscopy and energy transfer studies

A new family of covalently linked 'Sn(IV) porphyrin-anthracene'diad (1), triad (2) and tetrad (3) donor-acceptor (D-A) systems have been designed and synthesized in good-to-moderate yields. While diad 1 possesses one anthracene subunit at the peripheral (meso) position of the tin(IV) porphyrin scaffold, triad 2 possesses twotrans axial anthracene subunits at the tin(IV) centre. On the other hand, tetrad 3 is endowed with both the peripheral and axial anthracene subunits in its architecture. These D-A systems have been fully characterised by elemental analysis, FAB-MS, UV-Vis, 1H and 13C NMR and electrochemical methods. UV-Vis,NMR and redox data suggest the absence of intramolecular π-π interaction between the porphyrin and the anthracene/s in 1-3. Fluorescence from the anthracene subunit in 1 and 3 is found to be quenched in comparison with the fluorescence of free anthracene in four different solvents. This is not the case with compound 2. Excitation spectral data provides evidence for an intramolecular excitation energy transfer (EET) from the singlet anthracene to the porphyrin in 1 and 3. The energy transfer efficiency is in the order: 2 (almost negligible) < 3 (~30%) < 1 (nearly quantitative), with the peripheral anthracene → porphyrin pathway being largely favoured. This orientation dependence of EET could be analysed using Forster's dipole dipole mechanism

Cholate-interspersed porphyrin-anthraquinone conjugates: photonuclease activity of large sized, 'tweezer-like' molecules

In a new approach towards the development of a 'dual-wavelength dual-mechanism' type of photosensitizer for use in photodynamic therapy (PDT), covalently linked bichromophoric systems comprising of porphyrin (P) and anthraquinone (AnQ) subunits have been synthesized and fully characterized by FAB-MS, IR, UV-Visible and 1H NMR methods. The porphyrin donor and the anthraquinone acceptor subunits of these mono- or bis-intercalating hybrid molecules are interspersed with either cholate or polymethylene spacers. There exists minimal ground- and singlet-state interaction between the porphyrin and anthraquinone subunits in the giant-sized, cholate-interspersed P-AnQ systems as revealed by a comparison of their spectroscopic and electrochemical properties with those of the corresponding individual reference compounds. On the other hand, quenching of fluorescence observed for the P-AnQ systems endowed with polymethylene spacers has been interpreted in terms of a possible intramolecular electron transfer between the singlet porphyrin and the anthraquinone acceptor. When excited into their porphyrin absorption band maxima, each new P-AnQ system could generate singlet molecular oxygen in good-to-moderate yield. Wavelength-dependent photonuclease activity of these new bis-intercalating species has been examined

Pulmonary function changes in asymptomatic smokers - a community survey in Udupi, Karnataka, India

Background: Smoking has been labeled the most important preventable cause of a respiratory disease and its effects in a smoker are well established. A better understanding on the pulmonary function impairments in an asymptomatic smoker is the need of the hour. Objective: To study the pulmonary function changes in asymptomatic smokers and non- smokers and to establish the dose -effect relationship amongst asymptomatic smokers.Methods: A cross sectional survey was conducted in Udupi district of Karnataka, India. 140 men aged between 20 to 45 years with a BMI ranging from 18.5 to 29.9 Kg2 /m was enrolled in to the study. 70 subjects were asymptomatic smokers and the other 70 were non-smokers. Outcomes measured were standard spirometric measures for pulmonary function and symptoms like breathlessness, cough and sputum using a Breathlessness Cough Sputum scale.Results: The mean age (mean ± SD) of non-smokers and asymptomatic smokers enrolled was 34.7±5 and 33.8±5 years respectively. The mean smoking dose amongst the asymptomatic smokers was 15.74±5.5 pack years. FEV1 amongst the asymptomatic smokers showed a negative correlation with smoking dose (p<0.05) and there was a significant difference in FEV1, FVC, PEFR, MVV and FEF 25- 75 % (p<0.001) amongst the asymptomatic smokers and non-smokers.Conclusions: Asymptomatic smokers showed low values of pulmonary function parameters compared to those in non-smokers

Work related musculoskeletal disorders among medical laboratory professionals: a narrative review

Work related musculoskeletal disorders are common health problem and increasing cause of disability. Laboratory professionals are unique group of healthcare professionals who play an essential part in diagnosis and therapy planning and often their work is associated with potential health hazards. Objective of current study was to review literature on prevalence of work-related musculoskeletal disorders among medical laboratory professionals. Electronic databases and bibliographies were searched and identified papers evaluated against inclusion criteria. The searching strategy uncovered 13 reports. Total 7 studies were included for the review. A high degree of heterogeneity among studies was observed. The overall prevalence’s ranges from 40-60%. With neck being more prevalent 18-78%. However additional high quality studies are required in this area

Perceived attachment and problematic smartphone use in young people: mediating effects of self-regulation and prosociality

Background: Problematic use of smartphones is a challenge facing societies around the world. This phenomenon has been associated with negative socialization experiences through the impact they have on how the youth relates to their environment. This study was designed to examine parental and peer attachment, self-efficacy and prosocial reasoning as predictors of different attitudes towards online communication and problematic smartphone use. Method: 561 youth aged 14-20 years (Mage= 17.82; SD= 1.64; 67.7% Female) participated in an online survey. Results: Results indicated that an increase in self-efficacy or prosocial reasoning is correlated with a decrease in problematic smartphone use and attitudes towards online communication aimed at avoiding reality or constructing a more comfortable parallel social reality. Attachment to parents and peers had direct and indirect effects on problematic smartphone use and attitudes toward online communication through youth personal and social adjustment. Conclusions: Attachment plays a relevant role in the symptoms reduction of smartphone addiction and attitudes to online communication in youth, through its impact on self-efficacy perceptions and prosocial reasoning

Thermodynamic analysis of porphyrin binding to Momordica charantia (bitter gourd) lectin

Owing to the use of porphyrins in photodynamic therapy for the treatment of malignant tumors, and the preferential interaction of lectins with tumor cells, studies on lectin-porphyrin interaction are of significant interest. In this study, the interaction of several free-base and metalloporphyrins with Momordica charantia (bitter gourd) lectin (MCL) was investigated by absorption spectroscopy. Difference absorp-tion spectra revealed that significant changes occur in the Soret band region of the porphyrins on binding to MCL. These changes were monitored to obtain association constants (Ka) and stoichiometry of binding. The tetrameric MCL binds four porphyrin molecules, and the stoichiometry was unaffected by the presence of the specific sugar, lactose. In addition, the agglutination activity of MCL was unaffected by the presence of the porphyrins used in this study, clearly indicating that porphyrin and carbohydrate ligands bind at different sites. Both cationic and anionic porphyrins bind to the lectin with comparable affinity (Ka =103-105 m-1). The thermodynamic parameters associated with the interaction of several porphyrins, obtained from the temperature dependence of the Ka values, were found to be in the range: &#916; H&#176; = -98.1 to -54.4 kJ·mol-1 and &#916; S&#176; =-243.9 to -90.8 J·mol-1·K-1. These results indicate that porphyrin binding to MCL is governed by enthalpic forces and that the contribution from binding entropy is negative. Enthalpy-entropy compensation was observed in the interaction of different porphyrins with MCL, underscoring the role of water structure in the overall binding process. Analysis of CD spectra of MCL indicates that this protein contains about 13%&#945;-helix, 36%&#946;-sheet, 21%&#946;-turn, and the rest unordered structures. Binding of porphyrins does not significantly alter the secondary and tertiary structures of MCL

Cobalt(III), nickel(II) and ruthenium(II) complexes of 1,10-phenanthroline family of ligands: DNA binding and photocleavage studies

DNA binding and photocleavage characteristics of a series of mixed-ligand complexes of the type [M(phen)2LL]n+ (where M = Co(III), Ni(II) or Ru(II), LL = 1,10-phenanthroline (phen), phenanthroline-dione (phen-dione) or dipyridophenazine (dppz) andn = 3 or 2) have been investigated in detail. Various physico-chemical and biochemical techniques including UV/Visible, fluorescence and viscometric titration, thermal denaturation, and differential pulse voltammetry have been employed to probe the details of DNA binding by these complexes; intrinsic binding constants (Kb) have been estimated under a similar set of experimental conditions. Analysis of the results suggests that intercalative ability of the coordinated ligands varies as dppz>phen>phen-dione in this series of complexes. While the Co(II) and Ru(II) complexes investigated in this study effect photocleavage of the supercoiled pBR 322 DNA, the corresponding Ni(II) complexes are found to be inactive under similar experimental conditions. Results of detailed investigations carried out inquiring into the mechanistic aspects of DNA photocleavage by [Co(phen)2(dppz)]3+ have also been reported

Nonlinear absorption properties of 'axial-bonding' type tin(IV) tetratolylporphyrin based hybrid porphyrin arrays

The nonlinear absorption properties of 'axial-bonding' type hybrid porphyrin arrays based on a tin(IV) tetratolylporphyrin (SnTTP) scaffold are studied with picosecond and nanosecond pulses. The effect of different central metal atoms substituted adjacent to the tin(IV) porphyrin in the oligomer structure is discussed. In the picosecond regime the lifetimes of the excited singlet states and two-photon absorption (TPA) processes dominate leading to interesting switching of nonlinear absorption behaviour. The TPA cross-section (&#963;TPA) is found to be as high as 396 &#215; 10-46 cm4 s photon-1 molecule-1, for an oligomer with Sn and Ni porphyrin macrocycles. However, in the nanosecond regime the optical limiting performance has increased considerably with increasing number of porphyrins in the array and excited state absorption is found to play a major role