Application of the Heavy-Atom Effect for (Sub)microsecond Thermally Activated Delayed Fluorescence and an All-Organic Light-Emitting Device with Low-Efficiency Roll-off.

The feature of abundant and environmentally friendly heavy atoms (HAs) like bromine to accelerate spin-forbidden transitions in organic molecules has been known for years. In combination with the easiness of incorporation, bromine derivatives of organic emitters showing thermally activated delayed fluorescence (TADF) emerge as a cheap and efficient solution for the slow reverse intersystem crossing (rISC) problem in such emitters and strong efficiency roll-off of all-organic light-emitting diodes (OLEDs). Here, we present a comprehensive photophysical study of a tri-PXZ-TRZ emitter reported previously and its hexabromo derivative showing a remarkable enhancement of rISC of up to 9 times and a short lifetime of delayed fluorescence of 2 µs. Analysis of the key molecular vibrations and TADF mechanism indicates almost compete blockage of the spin-flip transition between the charge-transfer states of different multiplicity 3CT → 1CT. In such a case, rISC as well as its enhancement by the HA is realized via the 3LE → 1CT transition, where 3LE is the triplet state localized on the same brominated phenoxazine donor involved in the formation of the 1CT state. Interestingly, the spin-orbit coupling (SOC) with two other 3LE states is negligible because they are localized on different donors and not involved in 1CT. We consider this as an example of an additional "localization" criterion that completes the well-known El Sayed rule on the different nature of states for nonzero SOC. The applicative potential of such a hexabromo emitter is tested in a "hyperfluorescent" system containing a red fluorescent dopant (tetraphenyldibenzoperiflanthene, DBP) as an acceptor of Förster resonance energy transfer, affording a narrow-band red-emitting system, with most of the emission in the submicrosecond domain. In fact, the fabricated red OLED devices show remarkable improvement of efficiency roll-off from 2-4 times depending on the luminance, mostly because of the increase of the rISC constant rate and the decrease of the overall delayed fluorescence lifetime thanks to the HA effect.

Analysis of friction ridge evidence for trace amounts of paracetamol in various pharmaceutical industries by Raman spectroscopy.

The detection of potentially harmful substances presents a multifaceted challenge. On one hand, it can directly save lives, on the other, it can significantly aid and enhance police work, thereby increasing the effectiveness of investigations. The research conducted in this study primarily aims to identify paracetamol in fingerprints, considering situations involving direct contact of a person with paracetamol either chronically or in a single dose. The identification procedure presented, utilizing Raman spectroscopy, aims to rapidly detect the xenobiotic following ingestion by an individual, which involves touching the tablet with their fingers-this can be termed as touch evidence in forensic science investigations. Additionally, the authors focus on assessing the impact of additives present in drugs containing paracetamol as the main active ingredient. The screening results obtained will enable us to analyze the composition of drugs in terms of potentially toxic substances, and their influence on the physicochemical activity of the active substance. We successfully identified the paracetamol molecule using a noninvasive forensic trace detection method. Samples in the form of common drugs containing 500 mg of paracetamol were studied. Throughout the study, comprehensive validation of the method was ensured through the utilization of a statistical model, which excluded sensitivity to the presence of other substances, whether additives or from the external environment. The proposed approach to trace the content of substances in fingerprint using Raman scattering analysis provides a useful starting point to enhance current analytical methods not only in forensic science but also in toxicology.

Spectroscopic studies on the supramolecular interactions of methyl benzoate derivatives with p-sulfocalix[6]arene macrocycles.

This paper is a continuation of our previous research and aims to further investigate and elucidate the nature and mechanisms of noncovalent supramolecular interactions between four methyl benzoate derivatives (I-IV), which are capable of exhibiting Twisted Intramolecular Charge Transfer (TICT) and/or Excited State Intramolecular Proton Transfer (ESIPT)-type behavior, and chemical and biological nanocavities. Photophysical and photochemical properties of molecules I-IV in aqueous solution in the presence of well-recognized macrocyclic host p-sulfocalix[6]arenes (SCA[6]) have been studied using steady-state, time-resolved and 1H NMR spectroscopic techniques. The changes in the ground- and excited-state spectroscopic characteristics (absorption and fluorescence spectra, time-resolved fluorescence spectra, fluorescence decay times and 1H NMR spectra) undergo significant modifications upon encapsulation of the investigated methyl benzoate derivative in the macromolecular cavity. For the two compounds (I and II), the interactions with the macrocycles with a hydrophobic SCA[6] cavity lead to the formation of stable inclusion complexes with 1:1 stoichiometry, both in the ground and excited state, while the stoichiometry of the III-SCA[6] and IV-SCA[6] complexes in the ground and excited states is 1:2. The values of the equilibrium constants have been determined from the spectroscopic data using Benesi-Hildebrand and nonlinear regression procedures. The location of the organic molecule inside the SCA[6] has been investigated by 1H NMR experiments. The changes in macrocyclic compound-induced NMR chemical shifts clearly indicate that the chemical structure of inclusion complexes is very different for methyl benzoate derivative-SCA[6] and methyl benzoate derivative-CB[7] systems. Finally, we have shown, using time-dependent fluorescence Stokes shift, that very fast solvation dynamics of pure water is markedly different from that of the confined water molecule in SCA[6] system.

Surgical management of spontaneous intracranial hypotension syndrome: a literature review.

INTRODUCTION: Spontaneous intracranial hypotension (SIH) is a highly disabling but often misdiagnosed disorder. The optimal management options for patients with SIH remain uncertain. The aim of this study was to review studies reporting the management of SIH with a special emphasis on the surgical treatment of SIH including clinical trials, case series and case reports related to the issue of various neurosurgical procedures performed for SIH treatment. OBJECTIVE: The clinical outcomes of patients diagnosed with SIH treated with either only surgery or with surgery as the primary method of treatment were analysed. MATERIAL AND METHODS: The PubMed, Scopus and Google Scholar databases were searched according to the established criteria. RESULTS: The literature search revealed seven clinical trials, five case series and eight case reports regarding surgical treatment of patients diagnosed with SIH. Manuscripts reporting at least five individuals treated surgically for SIH were considered as case series. In most published articles, surgery provided clinical benefit, resulting in a success rate of 82.6-100% for complete relief of SIH symptoms. CONCLUSIONS: Our literature review has revealed that SIH can be diagnosed reliably by MRI and cisternography. The identification of the location of SIH is mandatory for its successful surgical treatment. The clinical outcome is related to the location of SIH in the spinal canal. Most often, cerebrospinal fluid leakage occurs in the thoracic region. Surgical treatment is very effective and the obtained treatment results are complete and permanent. of the location of SIH is mandatory for its successful surgical treatment. The clinical outcome is related to the location of SIH in the spinal canal. Most often, cerebrospinal fluid leakage occurs in the thoracic region. Surgical treatment is very effective and the obtained treatment results are complete and permanent.

Correction to Nonradiative Energy Migration in Spherical Nanoparticles Theoretical Model and Monte Carlo Study.

[This corrects the article DOI: 10.1021/acs.jpcc.2c02573.].

Nonconventional 1,8-Diazafluoren-9-One Aggregates for Green Light Enhancement in Hybrid Biocompatible Media.

Organic aggregates currently play a prominent role, mainly for their unique optoelectronic properties in the aggregated state. Such properties can be related to the aggregates' structure and the molecular packing mode. In the literature, we have well-established models of H and J aggregates defined based on the molecular exciton model. However, unconventional aggregates, the most unrecognized forms, have been generating interest among researchers recently. Within unconventional aggregation, aggregation-induced emission systems (AIE) are considered. In the present work, we discuss the effect of the forming of unconventional aggregation together with the change in dye concentration on the surface energy characteristics of the materials. All materials were prepared as hybrid biocompatible thin films where the matrix is TiO2 or TiO2/carbon nanowalls (CNWs) with the incorporated dye in the form of 1,8-diazafluoren-9-one (DFO). Using the time-resolved emission spectra and the determination of surface parameters from contact angle measurements, we indicated the correlation between the changes in such parameters and the concentration of DFO dye in two types of TiO2 and TiO2/CNW structures. To examine the propensity of DFO for aggregation, the internal energy of the dye was assessed in several aggregate structures using Quantum chemistry calculations. The results emphasize that DFO is an attractive structure in the design of new fluorophores due to its low molecular weight, the presence of a nitrogen atom that provides good coordination properties, and the ability to form hydrogen bonds. Our studies show that when using suitable matrices, i.e., rigid media, it forms the preferred forms of aggregates in the excited state, characterized by high emission efficiency in the band maximum of around 550 nm.

Spectroscopic evidence of fluorescence by 1,8-diazafluoren-9-one aggregates-A prospective new ultrasensitive method for fingerprint trace detection.

Friction ridge analysis would not have been one of the most recognized branches of forensics without molecular spectroscopy. The phenomenon of fluorescence is used on daily basis to develop latent fingerprints and to enhance those that are visible. The idea behind the research was to discover selected spectroscopic properties of 1,8-diazafluoren-9-one (DFO) in various environments. This fluorescent compound has been routinely used for decades to develop latent fingerprints due to its numerous advantages, but to this day, it has not been well-understood. Analysis of absorption, fluorescence, and excitation spectra of DFO in ethanol at high dye concentration allowed identification of aggregates in the excited state. A significant influence of the dye concentration on the fluorescence spectra and on the fluorescence excitation spectra was found. In particular, dye-host aggregation was found to be much stronger in a polar solvent. DFO aggregates are strongly fluorescent in ethanol, as can be seen from the steady-state emission spectra. The impact of excitation wavelength on the effect of fingerprint detection is presented. A new reaction medium has been proposed, ethanol, which is nontoxic in relation to the currently used one, methanol. The existence in this medium of DFO aggregates in the excited state, which significantly influences the identification of amino acids present in fingerprint traces, was observed, emitting in a wide spectral range (green light).

Surgical treatment of spontaneous intracranial hypotension syndrome secondary to the cervical cerebrospinal leak - a case report.

Spontaneous Intracranial Hypotension (SIH) is formed as a result of the leakage of cerebrospinal fluid (CSF) into the extradural space. The most common symptom caused by SIH is headache associated with changes in body position. Imaging, especially magnetic resonance imaging (MRI) of the head and spine with contrast, is the most important examination method in the diagnosis of SIH. In the case of no improvement after symptomatic treatment, surgery is very effective, especially in the case of finding the site of CSF leakage within the spinal canal. A CASE REPORT: We present a case of a 28-year-old patient with 2- month history of severe increasing headaches. The patient denied any head injuries, nasal CSF leakage or lumbar puncture in the past. The neurological examination showed no abnormalities. MRI of the head showed typical features of the intracranial hypotension syndrome. MRI of the cervical spine revealed potential sites for leakage of the cerebrospinal fluid at the C1-C2 level. The patient was qualified for surgical treatment - dural plastic surgery in the cervical section. After treatment the symptoms of intracranial hypotension resolved, and subsequent control MRI examinations showed regression of typical changes of the spontaneous intracranial hypotension. CONCLUSIONS: The authors would like to take notice that imaging diagnostics due to headaches should include MRI of the head and spine, as it is the most important test in diagnosing SIH. Moreover, surgical treatment is a quick and very effective method of treatment.

New Core-Shell Nanostructures for FRET Studies: Synthesis, Characterization, and Quantitative Analysis.

This work describes the synthesis and characterization of new core-shell material designed for Förster resonance energy transfer (FRET) studies. Synthesis, structural and optical properties of core-shell nanostructures with a large number of two kinds of fluorophores bound to the shell are presented. As fluorophores, strongly fluorescent rhodamine 101 and rhodamine 110 chloride were selected. The dyes exhibit significant spectral overlap between acceptor absorption and donor emission spectra, which enables effective FRET. Core-shell nanoparticles strongly differing in the ratio of donors to acceptor numbers were prepared. This leads to two different interesting cases: typical single-step FRET or multistep energy migration preceding FRET. The single-step FRET model that was designed and presented by some of us recently for core-shell nanoparticles is herein experimentally verified. Very good agreement between the analytical expression for donor fluorescence intensity decay and experimental data was obtained, which confirmed the correctness of the model. Multistep energy migration between donors preceding the final transfer to the acceptor can also be successfully described. In this case, however, experimental data are compared with the results of Monte Carlo simulations, as there is no respective analytical expression. Excellent agreement in this more general case evidences the usefulness of this numerical method in the design and prediction of the properties of the synthesized core-shell nanoparticles labelled with multiple and chemically different fluorophores.

Metastases to cranial base meningiomas. Clinical presentations and surgical outcomes. Literature overview.

Tumour-to-meningioma metastasis (TTMM) is an uncommon phenomenon, however repeatedly found in the literature. Meningiomas occur to be the most frequent target of metastatic expansion of systemic cancers. Meningiomas often vary in symptoms and treatment, and this largely depends on the tumour location. Due to their variable locations, they can be classified as convexity meningiomas, which includes falcine and parasagittal tumours, and cranial base, which includes tumours located in the olfactory groove, sphenoid wing, petrous bone and other cranial base locations. The aim of this study was to analyse all data regarding metastases to cranial base meningiomas. We performed a literature search to locate all cases of metastases to cranial base meningiomas in PubMed and Medline databases using the following key words: metastasis to meningioma, meningioma metastasis, and cranial base meningioma. We collected patient and cancer parameters, exact meningioma location and clinical presentations including characteristics which may suggest TTMM. We found 100 articles describing 111 patients of metastasis to cranial base meningioma. Among these articles, 55 cases (49.55%) included metastases to non-skull base meningiomas. In 24 cases (21.62%), the location of meningioma was not precisely described or other data were unavailable, in particular histopathological examination. The most common location of TTMM was sphenoid wing, which was found in 9 patients. The other locations included cerebellopontine angle in 5 patients, and tuberculum sellae in 3 cases. 81.25% cases of TTMM were reported in women, and the most common cancer origins were the breast (28.3%), lung (18.7%), kidney (9.38%) and prostate (9.38%). In two cases the metastatic origin was unclear, and in 15.6% of cases the patients were in remission for more than 1 year. In 78.1% of cases patients presented focal deficits, followed by increased intracranial pressure, and seizures. In almost one-third of cases, TTMM first appeared from a previously unknown cancer. Rapid clinical presentation of cranial nerve palsies may suggest the dual nature of intracranial pathology. The metastasis to cranial base meningioma should be suspected in patients with oncological background, regardless of meningioma parameters or cancer status.

Insight into Molecular Interactions of Two Methyl Benzoate Derivatives with Bovine Serum Albumin.

The nature and mechanisms of interaction between two selected methyl benzoate derivatives (methyl o-methoxy p-methylaminobenzoate-I and methyl o-hydroxy p-methylaminobenzoate-II) and model transport protein bovine serum albumin (BSA) was studied using steady-state and time-resolved spectroscopic techniques. In order to understand the role of Trp residue of BSA in the I-BSA and II-BSA interaction, the effect of free Trp amino acid on the both emission modes (LE-locally excited (I and II) and ESIPT-excited state intramolecular proton transfer (II)) was investigated as well. Experimental results show that the investigated interactions (with both BSA and Trp) are mostly conditioned by the ground and excited state complex formation processes. Both molecules form stable complexes with BSA and Trp (with 1:1 stoichiometry) in the ground and excited states. The binding constants were in the order of 104 M-1. The absorption- and fluorescence-titration experiments along with the time-resolved fluorescence measurements show that the binding of the I and II causes fluorescence quenching of BSA through the static mechanism, revealing a 1:1 interaction. The magnitude and the sign of the thermodynamic parameters, ΔH, ΔS, and ΔG, determined from van't Hoff relationship, confirm the predominance of the hydrogen-bonding interactions for the binding phenomenon. To improve and complete knowledge of methyl benzoate derivative-protein interactions in relation to supramolecular solvation dynamics, the time-dependent fluorescence Stokes' shifts, represented by the normalized spectral response function c(t), was studied. Our studies reveal that the solvation dynamics that occurs in subpicosecond time scale in neat solvents of different polarities is slowed down significantly when the organic molecule is transferred to BSA cavity.

Clinical presentation of neuroendocrine cancer metastasis to an anterior clinoid process meningioma invading superior orbital fissure. A case report.

Metastasis to a meningioma is an uncommon phenomenon however reported in the literature. Meningiomas are common primary intracranial tumours which most frequently occur to be a recepient of metastases. A 66-year-old female presented with rapid development of visual acuity and visual field loss in the right eye with ipsilateral oculomotor nerve palsy. Magnetic resonance imaging (MRI) showed well-defined tumour intensely enhanced with contrast like a typical skull base meningioma. The neuropathological examination revealed two different morphological fragments of the tumour. In the cell-rich part of the tumour, immunopositivity for CK, chromogranin, and SY were detected. The less cellular portion of the tumour, immunopositivity to epithelial membrane antigen (EMA) and vimentin were detected. To our knowledge, we present the first rare metastasis of neuroendocrine carcinoma to the medial sphenoid meningioma that preceded the clinical symptoms of systemic neuroendocrine carcinoma.

Vascular iatrogenic injury during lumbar disc surgery: a literature review.

Vascular injury during lumbar disc surgery was first reported as a complication in 1945 by Linton and White [32]. Injuries of the major blood vessels located anteriorly to the spine in the retroperitoneal space are rare but occur suddenly and are life-threatening. The authors present anatomo-topographical background of this complication, standards of diagnostic process and treatment on the base of literature as well the surgical and endovascular management of this complication. The authors performed a literature search for reported iatrogenic vascular injuries due to lumbar disc surgery. We were able to find 10 case series and 17 single case reports describing this rare but serious lumbar disc surgeryrelated complication. Overall, there were 159 patients who developed vascular injury due to lumbar disc surgery. The surgical exploration and repair has been done in 116 patients. In last decades due to rapid development of endovascular techniques this complication was repaired endovascular techniques in 21 patients. The most common lumbar level which resulted in iatrogenic vascular injury was L4-L5. There were reported 66 deaths and in 83 patients the postoperative period was uneventful. CONCLUSIONS: We would like to highlight the occurrence of this complication and introduction of rapid management to prevent the fatal outcome. Lumbar disc surgery is one of the most often performed procedures in neurosurgical wards. The awareness of this life-threatening complication should be known to all members of an operative team. The knowledge of proper management of this serious adverse event may save a patient's life.

Effect of Dimer Structure and Inhomogeneous Broadening of Energy Levels on the Action of Flavomononucleotide in Rigid Polyvinyl Alcohol Films.

The results of time-resolved fluorescence measurements of flavin mononucleotide (FMN) in rigid polyvinyl alcohol films (PVA) demonstrate that fluorescence intensity decays are strongly accelerated in the presence of fluorescent dimers and nonradiative energy transfer processes. The fluorescence decay originating both from H and J dimer states of FMN was experimentally observed for the first time. The mean fluorescence lifetimes for FMN dimers were obtained: τfl = 2.66 ns (at λexc = 445 nm) and τfl = 2.02 (at λexc = 487 nm) at λobs = 600 nm and T = 253 K from H and J state of dimers, respectively. We show that inhomogeneous orientational broadening of energy levels (IOBEL) affects the shape of the fluorescence decay and leads to the dependence of the average monomer fluorescence lifetime on excitation wavelength. IOBEL affected the nonradiative energy transfer and indicated that different flavin positioning in the protein pocket could (1) change the spectroscopic properties of flavins due to the existence of "blue" and "red" fluorescence centers, and (2) diminish the effectiveness of energy transfer between FMN molecules.

Rare iatrogenic iliac artery injury during lumbar disc surgery - a case report.

Damage to large abdominal vessels during lumbar discectomy surgery is a rare but life-threatening complication. A CASE REPORT: The authors present the case of a 57-year-old patient who received surgery for critical degenerative lumbal spinal stenosis on the L4-L5 level. The diagnosis was based on strong right sciatica and neurogenic claudication. A bilateral laminotomy from the right and a microdiscectomy were performed. During surgery, no bleeding from the intervertebral space was observed and blood pressure was low but stable from the beginning. After surgery, the patient was in good general and neurological condition, without preoperative right-sided sciatica. Within a few hours after the operation, the circulatory and respiratory systems were stable with normal saturation and the patient did not report shortness of breath. Paleness of the skin and mucous membranes was observed. Follow-up morphology tests performed at 6 and 10.5 hours after surgery showed a decrease in the level of erythrocytes. The patient had palpable tenderness in the left hypochondriac region. Suspicion of bleeding into the abdominal cavity from arteries or iliac veins was stated. Immediately, an angio-computed tomography (CT) of the abdominal cavity was performed, which confirmed the presence of a hematoma in the peritoneal space and a pseudoaneurysm of the left iliac artery. The patient was urgently transported to the Vascular Surgery Clinic, where a Y-type covered stent was implanted percutaneously into both iliac arteries. After the procedure, there were symptoms of ischaemia in the left lower extremity and intermittent claudication. A Doppler study showed signs of narrowing at the stent level on the left side. The patient was reoperated after a CT check-up and a second stent was implanted into the left iliac artery, which allowed vasodilation and true flow in the artery. CONCLUSIONS: The authors suggest that both the neurosurgeon and anaesthesiologist should have been aware of the possibility of such a rare but life-threatening complication as iliac vessel damage during lumbar discectomy surgery. A quick diagnosis and implementation of a proper procedure reduces the high mortality rate caused by this complication. In cases of a sudden unjustified drop in blood pressure during lumbar discectomy, an immediate laparotomy should be performed to find and repair the site of laceration of a vessel. In patients who are stable hemodynamically, performing an angio-CT function of the abdominal cavity is suggested and the damaged artery should be treated with a covered stent.

Vibrationally Assisted Direct Intersystem Crossing between the Same Charge-Transfer States for Thermally Activated Delayed Fluorescence: Analysis by Marcus-Hush Theory Including Reorganization Energy.

Thermally activated delayed fluorescence (TADF) has recently become an extensively investigated phenomenon due to its high potential for application in organic optoelectronics. Currently, there is still lack of a model describing correctly basic photophysical parameters of organic TADF emitters. This article presents such a photophysical model describing the rates of intersystem crossing (ISC), reverse ISC (rISC), and radiative deactivation in various media and emphasizing key importance of molecular vibrations on the example of a popular TADF dye 9,10-dihydro-9,9-dimethyl-10-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-acridine (DMAC-TRZ). The presented experimental and theoretical investigations prove that ISC and rISC can occur efficiently between the singlet and triplet states of the same charge-transfer nature (1CT and 3CT, respectively). In emitters with the orthogonal donor and acceptor fragments, such spin-forbidden 1CT ↔ 3CT transitions are activated by molecular vibrations. Namely, the change of dihedral angle between the donor and the acceptor affords reasonable spin-orbit coupling, which together with a small energy gap and reorganization energy enable 1CT ↔ 3CT transition rates reaching 1 × 107 s-1. Evidence of direct 1CT ↔ 3CT spin-flip and negligible role of a second triplet state, widely believed as a key parameter in the design of (r)ISC materials, change significantly the current understanding of TADF mechanism. In authors' opinion, photophysics, and molecular design principles of TADF emitters should be revised considering the importance of vibrationally enhanced 1CT ↔ 3CT transitions.

Dansyl-Labelled Ag@SiO2 Core-Shell Nanostructures-Synthesis, Characterization, and Metal-Enhanced Fluorescence.

The present work describes synthesis, characterization, and use of a new dansyl-labelled Ag@SiO2 nanocomposite as an element of a new plasmonic platform to enhance the fluorescence intensity. Keeping in mind that typical surface plasmon resonance (SPR) characteristics of silver nanoparticles coincide well enough with the absorption of dansyl molecules, we used them to build the core of the nanocomposite. Moreover, we utilized 10 nm amino-functionalized silica shell as a separator between silver nanoparticles and the dansyl dye to prevent the dye-to-metal energy transfer. The dansyl group was incorporated into Ag@SiO2 core-shell nanostructures by the reaction of aminopropyltrimethoxysilane with dansyl chloride and we characterized the new dansyl-labelled Ag@SiO2 nanocomposite using transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR). Additionally, water wettability measurements (WWM) were carried out to assess the hydrophobicity and hydrophilicity of the studied surface. We found that the nanocomposite deposited on a semitransparent silver mirror strongly increased the fluorescence intensity of dansyl dye (about 87-fold) compared with the control sample on the glass, proving that the system is a perfect candidate for a sensitive plasmonic platform.

Influence of a 4'-substituent on the efficiency of flavonol-based fluorescent indicators of ß-glycosidase activity.

This article presents novel fluorescent probes, based on the excited-state intramolecular proton transfer (ESIPT) phenomenon and flavonols, sensitive to the action of specific glycosidases. 4'-Substituted flavonols were synthesized, using various approaches, and glycosylated with d-glucose, N-acetyl-d-glucosamine and d-glucuronic acid. Evaluation of the ß-glycosidase activities was performed in neutral and acidic pH. In all the cases examined, an acidic environment accelerated enzymatic hydrolysis. It was demonstrated that the 4'-chloroflavonyl glycosides of all sugars tested, both in neutral and acidic pH, are the ones most sensitive to the presence of hydrolase. In turn, 4'-dimethylaminoflavonyl glucoside is not sensitive to glucosidase action at all. Generally, the rate of enzymatic hydrolysis increases as the electron-withdrawing nature of the 4'-substituent increases. An exception is the trifluoromethyl group which, in spite of having the most favourable Hammett constant, does not contribute enough to increase the rate of hydrolysis of its glucoside. The presented experimental results are supported by the electrostatic potential (ESP) analysis and related to the mechanisms of glycoside bond enzymatic hydrolysis.

The Luminescence of 1,8-Diazafluoren-9-One/Titanium Dioxide Composite Thin Films for Optical Application.

The investigation of innovative label-free α-amino acids detection methods represents a crucial step for the early diagnosis of several diseases. While 1,8-diazafluoren-9-one (DFO) is known in forensic application because of the fluorescent products by reacting with the amino acids present in the papillary exudate, its application for diagnostic purposes has not been fully investigated. The stabilization of DFO over a transparent substrate allows its complexation with biomolecules for the detection of α-amino acids. In this study, DFO was immobilized into a titanium dioxide (TiO2) matrix for the fluorescence detection of glycine, as a target α-amino acid (a potential marker of the urogenital tract cancers). The DFO/TiO2 composite was characterized by atomic force microscopy, spectroscopic ellipsometry, fluorescence spectroscopy and fluorescence microscopy. The performed fluorescent studies indicate spectacular formation of aggregates at higher concentration. The measurements performed using various fluorescence and microscopic techniques together with the suitable analysis show that the aggregates are able to emit short-lived fluorescence.

Time-resolved emission spectra of 4-dimethylamino-4'-cyano-stilbene and resveratrol in high viscosity solvents and silica matrices.

Time-resolved emission spectra of 4-dimethylamino-4'-cyano-stilbene (DMACS) and 3,5,4'-trihydroxy-stilbene (resveratrol, RSV) in propylene glycol and in rigid silica xerogel matrix at 23°C were studied. For the polar molecule DMACS in propylene glycol, a 66nm shift of maximum wavelength of emission spectra was observed within 1ns after excitation, and most of the shift occurred during the first 200ps. For resveratrol in propylene glycol no such a shift was observed. The rigid silica environment eliminates some deactivation pathways and stabilizes spectroscopic properties of both molecules. Spectral properties of nonpolar and high dipole moment molecules in viscous liquids and rigid environments are compared. Results are explained on the basis of intramolecular processes and solute-solvent relaxation, as well.