Characterization of subdomain IIA binding site of human serum albumin in its native, unfolded, and refolded states using small molecular probes

Subdomain IIA binding site of human serum albumin (HSA) was characterized by examining the change in HSA fluorescence in the native, unfolded, and refolded states. The study was carried out in the absence and presence of small molecular probes using steady-state and time-resolved fluorescence measurements. 2-Pyridone, 3-pyridone, and 4-pyridone bear similar molecular structures to those found in many drugs and are used here as probes. They are found to specifically bind in subdomain IIA and cause a reduction in the fluorescence intensity and lifetime of the Trp-214 residue in native HSA which is located in the same subdomain. The efficiency of energy transfer from Trp-214 fluorescence to the probes was found to depend on the degree of the spectral overlap between the donor's fluorescence and the acceptor's absorption. After probe binding in subdomain IIA, the distance between the donor and acceptor was calculated using Forster theory. The calculated quenching rate constants and binding constants were also shown to depend on the degree of spectral overlap. The results point to a static quenching mechanism operating in the complexes. Denaturation of HSA in the presence of guanidine hydrochloride (GdnHCl) starts at [GdnHCl] > 1.0 M and is complete at [GdnHCl] > or = 6.0 M. Upon unfolding, two fluorescence peaks were observed. One peak was assigned to the fluorescence of Trp-214 in a polar environment, and the other peak was assigned to tyrosine fluorescence. A reduction of the fluorescence intensity of the two peaks upon binding of the probes to the denatured HSA indicates that Tyr-263 in subdomain IIA is one of the tyrosine residues responsible for the second fluorescence peak. The results were confirmed by measuring the fluorescence spectra and lifetimes of denatured HSA at different excitation wavelengths, and of L-tryptophan and L-tyrosine free in buffer. The measured lifetimes of denatured HSA are typical of tryptophan in a polar environment and are slightly reduced upon probe binding. Dilution of the denatured HSA by buffer results in a partial refolding of subdomain IIA. This partial refolding is attributed to some swelling of the binding site caused by water. The swelling prevents a full recovery from the denatured state.     

Silver-catalyzed spirolactonization: first synthesis of spiroisoindole-γ-methylene-γ-butyrolactones

γ-Acetylenic carboxylic acids are cyclized to spirolactones under mild conditions, in the presence of Ag₂CO₃ catalyst. The corresponding spiro-5-alkylidene-γ-butyrolactones were isolated in high yields, and this process constitutes an easy and efficient route to analogous structures of natural products of biological interest.     

Luminescence decay kinetics of Eu<Superscript>3+</Superscript> ions in phosphate glasses of different composition under photo- and electron excitations

The influence of matrix composition, coactivators, and excitation method on the luminescence kinetics of Eu³⁺ ions in lithium–phosphate and lithium–phosphate–borate glasses activated by Eu, Eu/Tb, and Eu/Dy is studied. Luminescence is excited by a high current electron beam and a xenon lamp. It is found that, under photoexcitation, the europium luminescence decays more slowly than under electronic excitation. Depending on the content of cation modifiers ZnO and Li₂O, the decay time decreases with increasing amount of ZnO. The decay time weakly depends on the europium concentration. The decay of the luminescence of europium ions is well described by the Inokuti–Hirayama model.     

Effect of synthesis conditions on preparation of mesoporous titania-silica by a modified sol-gel technique using a cationic surfactant

Titania-silica mesoporous materials have been synthesized by a modified sol-gel technique using a cationic surfactant. The synthesis process was studied using statistical design of experiments to achieve the best conditions for titania-silica preparation. The synthesized materials were characterized by XRD, FT-IR, SEM and surface area measurements. The XRD and SEM results showed an amorphous structure of titania-silica. The surface area measurements using nitrogen adsorption showed type-IV isotherms which indicate the formation of mesoporous structure. A high surface area can be obtained (685 m²/g). The crystal size of titania-silica calculated using Scherrer’s equation was found to be in the range 8–15 nm.     

The study of the conversion of intercalated compounds synthesized from a sol-gel procedure

Intercalated materials containing iron and carbonate species were synthesized in this work to study their hydrolysis and condensation from sol to gel transition. The former material was designated as PV (perovskite) and the latter HT (hydrotalcite). Another sample containing neither of the indicated ions was designated as AlMg(OH)₅ (aluminum magnesium hydroxide). The conversion energy of these materials for the hydrolysis and condensation reaction during the transition was estimated to be ≈14 cal/mol, much lower than the hydration energy of 10–14 kcal/mol computed using molecular dynamic simulation from the previous work. The energy consumed was interpreted as equivalent to the drop of temperature due to the endothermic reaction. PV material exhibited the highest swelling ratio, amounting to 76% from its dried weight, demonstrating its ability to intercalate water readily. HT sample, on the other hand, was completely saturated and did not dilate.     

Multiplexed quantitation of endogenous estrogens and estrogen metabolites in human peritoneal fluid

Endogenous estrogens and estrogen metabolites (EM) in human peritoneal fluid may play an important role in health and disease, yet little is known regarding their types and levels present in human peritoneal fluid, primarily due to the lack of an analytical method that is capable of directly quantifying their absolute abundances. In this report, we describe the application of a capillary LC-MS/MS method for identifying and quantifying biologically active and total endogenous EM in human peritoneal fluid. The method requires only 50 muL of peritoneal fluid, yet can quantify 13 distinct EM. Calibration curves for each EM were linear over a 10(3)-fold concentration range and the lower LOQ was 50 fg on-column. For a charcoal stripped human peritoneal fluid sample containing 10 pg/mL of each EM, accuracy ranged from 83 to 118%, and intrabatch precision ranged from 0.2 to 4.4% RSD and interbatch precision ranged from 5.5 to 15.5% RSD. The analyses of human female peritoneal fluid shows that at least 10 biologically active and 11 total endogenous EM can be positively identified and quantitatively measured. Many of the biologically active forms are present in high abundance and possess distinct biological activities which warrant further study. Although micellar EKC gave baseline separation of a standard mixture of 10 EM, the LOQs using UV detection were not suitable for the assay of the low level estrogens in biological samples.     

An investigation of dielectric resonator antenna produced from silicon (100) enhanced by strontium doped-barium zirconate films

Dip-coated Ba_1−x Sr _x ZrO₃ thick films with different Ba/Sr ratios (x = 0.0, 0.1, 0.3, 0.5, 0.7 and 0.9) were fabricated on Si (100-orient) substrate at a low temperature of 800 °C via the sol gel method. The experimental results show that dielectric resonator (DR) properties of Ba_1−x Sr _x ZrO₃ films depend on the different Ba/Sr ratios. For structural characterization, the X-ray analysis revealed that phase transformation was affected by the increase in Sr concentrations for heat treatment at 800 °C. The films were crystalline and of single phase. The thickness of one BSZ film is around 1.259 μm when measured using the field emission scanning electron microscope. The BSZ film’s surface morphology as indicated by the atomic force microscopy showed the mean grain size to be in the range of 2.56 to 94.34 μm, and the surface roughness (RMS) was recorded to be between 2.35 to 19.64 nm. The dielectric resonator (DR) properties were measured using a network analyzer. By introducing Ba_1−x Sr _x ZrO₃ (BSZ) films on the high dielectric Si (100-orient) substrate, better frequency stability was achieved i.e. within the range of 8–10 GHz. Measured results show that Si (100-orient) DRA has a 10 dB impedance bandwidth of 4.11% at 9.34 GHz and the BSZ improved this to 11.34% with x = 0.7 at 9.15 GHz. The radiation pattern was observed to be stable throughout the operating frequency and holds good potential for DR applications.     

The effect of carbonisation temperatures on nanoporous characteristics of activated carbon fibre (ACF) derived from oil palm empty fruit bunch (EFB) fibre

Activated carbon fibre (ACF) is a nanoporous material which is useful for various important applications such as safe biogas and natural gas storage as well as heavy/precious metals removal and recovery. It is commonly produced from synthetic fibres such as rayon, polyacrylnitrile and pitch mainly derived from petroleum products, which are less environmental friendly. Besides, cost of ACF production is high due to the high burnt off percentage of such expensive raw materials. As an alternative, natural fibre of oil palm empty fruit bunch was used as a raw material for ACF preparation. Thermogravimetric analysis was carried out with two different gases, i.e. nitrogen gas and oxygen gas in order to observe pyrolysis and combustion behaviours in different gases. Carbonisation temperatures were then identified from the peaks of derivative thermogravimetry results. Different carbonisation temperatures (85?C200?°C) were chosen to carbonise the EFB fibre to observe the effect of carbonisation temperatures on the nanoporous characteristics, i.e. surface area, pore size distribution and pore volume of the ACF produced. Good nanoporous characteristics such as surface area up to 2,740?m²/g of the ACF prepared were observed, suggesting EFB fibre as an excellent candidate to replace synthetic fibre for ACF production. The discussion of relationship between thermal characteristics and nanopores in ACF derived from EFB were also included in this study.     

Andrographolide Induces G2/M Cell Cycle Arrest and Apoptosis in Human Glioblastoma DBTRG-05MG Cell Line via ERK1/2 /c-Myc/p53 Signaling Pathway

Human glioblastoma multiforme (GBM) is one of the most malignant brain tumors, with a high mortality rate worldwide. Conventional GBM treatment is now challenged by the presence of the blood–brain barrier (BBB), drug resistance, and post-treatment adverse effects. Hence, developing bioactive compounds isolated from plant species and identifying molecular pathways in facilitating effective treatment has become crucial in GBM. Based on pharmacodynamic studies, andrographolide has sparked the interest of cancer researchers, who believe it may alleviate difficulties in GBM therapy; however, it still requires further study. Andrographolide is a bicyclic diterpene lactone derived from Andrographis paniculata (Burm.f.) Wallich ex Nees that has anticancer properties in various cancer cell lines. The present study aimed to evaluate andrographolide’s anticancer effectiveness and potential molecular pathways using a DBTRG-05MG cell line. The antiproliferative activity of andrographolide was determined using the WST-1 assay, while scratch assay and clonogenic assay were used to evaluate andrographolide’s effectiveness against the cancer cell line by examining cell migration and colony formation. Flowcytometry was also used to examine the apoptosis and cell cycle arrest induced by andrographolide. The mRNA and protein expression level involved in the ERK1/2/c-Myc/p53 signaling pathway was then assessed using qRT-PCR and Western blot. The protein–protein interaction between c-Myc and p53 was determined by a reciprocal experiment of the co-immunoprecipitation (co-IP) using DBTRG-05MG total cell lysate. Andrographolide significantly reduced the viability of DBTRG-05MG cell lines in a concentration- and time-dependent manner. In addition, scratch and clonogenic assays confirmed the effectiveness of andrographolide in reducing cell migration and colony formation of DBTRG-05MG, respectively. Andrographolide also promoted cell cycle arrest in the G2/M phase, followed by apoptosis in the DBTRG-05MG cell line, by inducing ERK1/2, c-Myc, and p53 expression at the mRNA level. Western blot results demonstrated that c-Myc overexpression also increased the production of the anti-apoptotic protein p53. Our findings revealed that c-Myc and p53 positively interact in triggering the apoptotic signaling pathway. This study successfully discovered the involvement of ERK1/2/c-Myc/p53 in the suppression of the DBTRG-05MG cell line via cell cycle arrest followed by the apoptosis signaling pathway following andrographolide treatment.