Ultrafast Processes in Upper Excited Singlet States of Free and Caged 7-Diethylaminothiocoumarin.

The photochemistry and photophysics of thiocarbonyl compounds, analogues of carbonyl compounds with sulfur, have long been overshadowed by their counterparts. However, recent interest in visible light reactions has reignited attention toward these compounds due to their unique excited-state properties. This study delves into the ultrafast dynamics of 7-diethylaminothiocoumarin (TC1), a close analogue of the well-known probe molecule coumarin 1 (C1), to estimate intersystem crossing rates, understand the mechanisms of fluorescence and phosphorescence, and evaluate TC1's potential as a solvation dynamics probe. Enclosing TC1 within an organic capsule indicates its potential applications, even in aqueous environments. Ultrafast studies reveal a dominant subpicosecond intersystem crossing process, indicating the importance of upper excited singlet and triplet states in the molecule's photochemistry. The distinct fluorescence and phosphorescence origins, along with the presence of closely spaced singlet excited states, support the observed efficient intersystem crossing. The sulfur atom alters the excited-state behavior, shedding light on reactive triplet states and paving the way for further investigations.

Clinico-Laboratory Profile of Hypertriglyceridemia Thalassemia Syndrome: A Case Series in a Paediatric Tertiary Care Centre.

BACKGROUND: Increased hemolysis and repeated blood transfusion trigger oxidative stress resulting in numerous adverse effects in beta-thalassemia patients. Extreme elevation of triglyceride level is a rare clinical entity seen in these patients. It is presumed to be caused due to an increase in oxidative stress and is termed Hypertriglyceridemia Thalassemia Syndrome. OBJECTIVES: To assess the clinical and laboratory characteristics of beta-thalassemia patients presenting with hypertriglyceridemia and its correlation with the pre-transfusion hemoglobin level.  Methods: This hospital record-based retrospective study was conducted at the Dr B C Roy Post Graduate Institute of Paediatric Sciences, Kolkata, India. The study comprised 12 pediatric beta-thalassemia patients whose plasma appeared milky or chylous during a complete hemogram. Clinical examination and laboratory investigations were done to describe their clinico-laboratory features. A whole exome sequencing was carried out to assess their genetic background. Blood hemoglobin and serum triglyceride estimation was carried out initially and at follow-up to determine any correlation between the two.  Results: Out of 1482 patients, 12 (0.80 %) were diagnosed with Hypertriglyceridemia Thalassemia Syndrome. The median age of presentation was 12.5 months (Q1:10 months, Q3:14 months)., and the pretransfusion hemoglobin was 4.82 ± 1.16 g/dL. The lipid profile showed a triglyceride level of 858.3 ± 198.4 mg/dl and a total cholesterol level of 117.4 ± 16.15 mg/dl. Analysis revealed that the triglyceride levels were negatively correlated with the pretransfusion hemoglobin level (repeated measures correlation (rmcorr) = -0.65, 95% CI [-0.794, -0.425], p < 0.001). A genetic study highlighted c.92+5G>C as the commonest mutation. CONCLUSION: Hypertriglyceridemia was a rare presentation in transfusion-dependent beta-thalassemia patients. The serum triglyceride level significantly reduced when blood transfusion at regular intervals restored the patient's hemoglobin level.

Rationalizing the Unexpected Sensitivity in Excited State Lifetimes of Adenine to Tautomerization by Nonadiabatic Molecular Dynamics.

The remarkable photostability of canonical nucleobases makes them ideal building blocks for DNA and RNA. Even minor structural changes are expected to lead to drastic alteration of their subpicosecond excited state lifetimes. However, it is interesting to note that while the 9H- and 7H-amino tautomers of adenine possess drastically different lifetimes, 9H- and 7H-keto guanine possess similar excited state lifetimes. With an aim to explain this unexpected difference in sensitivity of lifetimes to tautomerization, we have investigated the excited state relaxation mechanism of UV-excited adenine and guanine tautomers using surface hopping based nonadiabatic molecular dynamics. We find that internal conversion in both guanine tautomers is almost barrierless while both adenine tautomers encounter significant barriers before they can deactivate. Moreover, the major deactivation channel (C2-puckering) in 9H-amino adenine is overall more efficient than the one (C6-puckering) in the 7H-amino form. We trace this difference to the frequent rotation of the amino group which disrupts its conjugation with the heterocyclic ring thereby reducing the strength of nonadiabatic coupling and, hence, delaying internal conversion.