Intermembrane cholesterol transfer: Role of sterol carrier proteins and phosphatidylserine

The effect of phosphatidylserine and sterol carrier proteins on cholesterol exchange was determined using an assay not requiring separation of donor and acceptor membrane vesicles. Sterol carrier protein-2 (SCP₂, also called nonspecific lipid transfer protein), but not fatty acid binding protein (FABP, also called sterol carrier protein), enhanced the initial rate of sterol exchange between neutral zwitterionic phosphatidylcholine small unilamellar vesicles (SUV) 2.3-fold. Phosphatidylserine at 10 mol% increased the initial rate of spontaneous and of SCP₂-mediated (but not FABP-mediated) sterol exchange by 22% and 44-fold, respectively. The SCP₂ potentiation of sterol transfer was dependent on SCP₂ concentration and on phosphatidylserine concentration. The SCP₂-mediated sterol transfer was inhibited by a variety of cations including KCl, divalent metal ions, and neomycin. The data suggest that SCP₂ increase in activity for sterol transfer may be partly ascribed to charge on the phospholipid. A portion of this work was presented as an abstract: Nemecz, G., Butko, P., and Schroeder, f. (1989)Biophysical Journal 55, 137a.     

A nonradiative energy transfer fluorescence spectroscopy study of poly(vinyl chloride)/poly(methyl methacrylate) blends

The miscibility of poly(vinyl chloride)/atactic poly(methyl methacrylate (PVC/a-PMMA) blends was investigated by nonradiative energy transfer fluorescence spectroscopy using naphthalene-labeled PVC (PVC-N) with anthracene-labeled PMMA (PMMA-A), or anthracene-labeled PVC (PVC-A) with carbazole-labeled PMMA (PMMA-C). The two sets of results indicate an increase in energy transfer efficiency, corresponding to an increase in blend miscibility, as the PVC concentration increases and, more importantly, demonstrate that the same information about blend miscibility can be obtained using different donor-acceptor chromophore pairs and by changing the polymer to which the donor or the acceptor is attached. The effect of the tacticity of PMMA on its miscibility with PVC was also investigated using PMMA-C and PVC-A labeled polymers. The results confirm that PVC/a-PMMA blends are more miscible than PVC/i-PMMA blends over a large range of compositions.     

The effect of solid content on latex coalescence and film formation: Steady-state energy transfer study with fluorescence labeled polymers

The steady-state fluorescence technique was used to examine the healing and interdiffusion of polymer molecules as a function of solid content during annealing of latex films above the glass transition (T_g). Films were prepared from a mixture of naphthalene (N)- and pyrene (P)-labeled poly(methy methacrylate) (PMMA) latex particles. Above T_g, interdiffusion of polymer chains was observed by detecting the steady-state energy transfer from excited naphthalene to pyrene molecules. Various latex films with different latex content were used to measure the critical occupation percent for the reliable steady-state fluorescence measurements. Diffusion activation energies in these latex films were measured and found to be around 30 kcal/mol, which was attributed to the backbone motion of PMMA chains. © 1996 John Wiley & Sons, Inc.     

Lipid metabolism of the yellow clam,Mesodesma mactroides: 2-Polyunsaturated fatty acid metabolism

The fate of labeled linoleic, α-linolenic, and higher homologs of α-linolenic acid administered to the yellow clam,Mesodesma mactroides, was investigated. It was found that the clam incorporated the acids dissolved in sea water and converted 18∶2 (n−6) into 20∶2 (n−6) and 18∶3 (n−3) into 18∶4 (n−3) and 20∶3 (n−3). The addition of casein hydrolysate to the sea water increased the desaturation capacity of the clam and allowed the conversion of 18∶2 (n−6) into 18∶3 (n−6) to be demonstrated. An enhanced desaturation of 18∶3 (n−3) into 18∶4 (n−3) was also demonstrated. After 12 hr administration of the acid, no radioactivity was found in arachidonic, 20∶5 (n−3), or 22∶6 (n−3). Feeding the clams a culture ofPhaeodactylum tricornutum previously incubated with 1-¹⁴C-α-linolenic acid demonstrated that all the homologs of the α-linolenic series were found in the clam without any important changes. Six hour administration of labeled linolenic acid resulted in the incorporation of the acid into diglycerides and phospholipids. Member of the carrera del Investigador Cientifico of the Consejo Nacional de Investigaciones Cientificas y Tecnicas     

Lipid and fatty acid composition of the endogenous energy sources of striped bass (Morone saxatilis) eggs

The unique physiological flexibility of the early life stages of striped bass is attributed to the calorierich endogenous energy sources of the striped bass egg. Eggs of different aged striped bass from geographically separate populations were examined for lipid and fatty acid compositions and were found to be basically similar. Yolk components of the eggs contained significantly less total lipid than oil globules, were more diverse in lipid class composition and consisted mostly of polar lipids. Oil globules were entirely lipid material consisting predominantly of steryl/wax esters. Fatty acid compositions of yolk and oil globules differed according to their respective lipid compositions. The functional significance of these lipids is discussed in relation to the ecological context of the early life stages.     

A corrosion study and minority carrier diffusion length determination of n-type SnS2 and SnSSe

Corrosion behaviour of n-type SnS₂ and SnSSe single crystals in aqueous solutions has been studied. It has been shown that SnS₂ and SnSSe undergo a corrosion reaction in the dark when electrolytes contain oxidizing agents such as Fe(CN)³⁻₆ (KOH) and Ce⁴⁺ (H₂SO₄). Corrosion has a chemical nature. Values of absorption coefficient and hole diffusion length has been determined for both materials using the Gärtner model. A hole diffusion length of (2±0.5)×10⁻⁵ cm and (5±2)×10⁻⁷ cm was obtained, respectively, for samples prepared by Bridgman and Transport methods. The difference in hole diffusion length is explained by the existence of recombination centers produced by the transporting agent in the crystal bulk. A quantum yield of greater than one is found for SnSSe at high photon energies (greater than 2eV). This phenomenon has been explained by activation of a second electron from surface states above the valence band to the surface states below the conduction band.     

Swelling activation energy of κ‐carrageenan in its gel state: A fluorescence study

A steady‐state fluorescence technique was employed to study the swelling of κ‐carrageenan gels at various temperatures. Pyranine was used as a fluorescence probe. The fluorescence intensity of pyranine was measured during the insitu swelling process of κ‐carrageenan gels. The fluorescence intensity increased exponentially as the swelling time increased. The increase in the fluorescence intensity was modeled with the Li–Tanaka equation, from which the swelling time constants and cooperative diffusion coefficients were determined. The swelling time constants decreased and the cooperative diffusion coefficients increased as the swelling temperature was increased. The swelling activation energies were measured to be 47.05 kJ/mol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Lipid metabolism of the yellow clam,Mesodesma mactroides: 3-Saturated fatty acids and acetate metabolism

The fate of labeled palmitate, stearate, and acetate administered to the yellow clam,Mesodesma mactroides, was investigated. 1-¹⁴C palmitic and 1-¹⁴C stearic acids were oxidized to CO₂ to a limited extent. They were mainly incorporated in diacylglycerols and triacylglycerols and were converted to higher homologs. After administration, palmitic acid was converted to stearic and oleic acids, whereas administered stearic acid was converted to 18∶1, 18∶2, 20∶1, and 20∶2 acids. Labeled acetate was readily included by the clam in 12∶0, 14∶0, 14∶1, 15∶0, 16∶1, 16∶1, 16∶2, 18∶2, 18∶1, 18∶2, 20∶1, 20∶2, and 20∶3 acids.     

A kinetic model for evaluating the dependence of the quantum yield of nano-TiO2 based photocatalysis on light intensity, grain size, carrier lifetime, and minority carrier diffusion coefficient: Indirect interfacial charge transfer

A model based on spherical TiO₂ nanoparticles was developed to study heterogeneous photocatalysis based on TiO₂ in the case of indirect interfacial charge transfer. In this model, the effect of light intensity (I₀), grain size (r₀), carrier lifetime (τ_p), and minority carrier diffusion coefficient (D_p) on the quantum yield (QY) of photocatalytic reactions was investigated in detail. Under conditions of sufficiently low incident-light intensity, the QY was found to be ∝I₀, while it decreased rapidly with an increase in I₀. In addition, the QY went to zero at a critically high light intensity. Furthermore, the QY was found to decrease with increasing r₀ due to the bulk-recombination loss, and the effect of r₀ on the QY became increasingly stronger with the increase in I₀. The QY decreased with the decrease in τ_p and D_p, which was more apparent at the critically high I₀. Under conditions of low [(RH₂)_aq], the QY increased with an increase in [(RH₂)_aq], while it remained nearly constant at high [(RH₂)_aq] due to the fact that the photoinduced electron interfacial transfer became the limiting step for photocatalytic reactions in the case of high [(RH₂)_aq].     

Zero-thermal-quenching of LiAl5O8: Eu2+, Mn2+ phosphors by energy transfer and defects engineering

The photoluminescence behavior of inorganic phosphors is generally influenced by thermal stability, which determines the luminescence efficiency of the corresponding devices. Here, a series of Eu²⁺, Mn²⁺ co-doped LiAl₅O₈ blue-green-emitting phosphors with thermal robust are successfully fabricated. The concentration-dependent emission spectra and the decay curves of the as-obtained LiAl₅O₈: Eu²⁺, Mn²⁺ samples manifest the occurrence of the energy transfer from Eu²⁺ to Mn²⁺ ions via dipole-dipole interaction, and the corresponding emitted colors are gradually modulated from blue to green under the excitation of 310 nm. Moreover, the zero-thermal-quenching luminescence is observed when the operation temperature is up to 423 K, which is attributed to the energy release from the trapping centers to emitting centers (Eu²⁺ and Mn²⁺) at high temperature. Furthermore, a warm white light-emitting diodes (WLEDs) device with correlated color temperature of 5061 K, a color rendering index of 80.6 and long-term stability is fabricated by combining UV LED chip (λ_ex = 310 nm), as-obtained LiAl₅O₈: Eu²⁺, Mn²⁺ phosphor, commercially available red phosphor and green phosphor. These results prove the potential application of the as-obtained LiAl₅O₈: Eu²⁺, Mn²⁺ phosphor for UV-pumped WLEDs devices.     

A comparative study of the phospholipids and fatty acids of some insects

Phospholipids of 27 species of insects representing 6 orders and 20 families were examined by DEAE cellulose column chromatography to determine the choline/ethanolamine phosphoglyceride ratios, and by gas chromatography to determine the constituent fatty acids. The phosphorus in the ethanolamine phosphoglycerides accounted for approximately 50% of the total lipid phosphorus in aphids (Homoptera) and in all but one family of Diptera (flies) examined while the phosphorus in the choline phosphoglycerides accounted for only about 25%. Ethanolamine and choline phosphoglycerides were present in approximately equal proportions in one family of Diptera and in the Coleoptera (beetles) examined. In the other insects examined choline phosphoglycerides predominated, ethanolamine phosphoglycerides comprising only about 25–30% of total lipid phosphorus as they do in most mammalian tissues. Diptera in which ethanolamine phosphoglycerides were the major phosphatides were also characterized by high proportions of fatty acids less than 18 carbons long, particularly palmitoleic acid, in the neutral lipids. Aphids are characterized by a preponderance of 14-carbon fatty acids. The evidence suggests that predominance of ethanolamine phosphoglycerides is associated with a preponderance of shorter chain fatty acids in the neutral lipids. Differences also exist between Diptera and other insects in the fatty acid compositions of different phosphatides, particularly with respect to the distribution of 18-carbon acids. The compositions observed in insects that contained large amounts of the choline phosphoglycerides are similar to those found in vertebrates. Similarities in fatty acid composition of the choline phosphoglycerides in such widely divergent organisms suggest that the fatty acids may play a greater role in phospholipid function than has heretofore been demonstrated. Contribution Number I.P.R.I. 74.     

Luminescence properties and energy transfer investigations of Sr2B2O5:Ce3+,Tb3+ phosphors

Ce³⁺ and Tb³⁺ co-doped Sr₂B₂O₅ phosphors were synthesized by the solid-state method. X-ray diffraction (XRD) was used to characterize the phase structure. The luminescent properties of Ce³⁺ and Tb³⁺ co-doped Sr₂B₂O₅ phosphors were investigated by using the photoluminescence emission, excitation spectra and reflectance spectra, respectively. The excitation spectra indicate that this phosphor can be effectively excited by near ultraviolet (n-UV) light of 317 nm. Under the excitation of 317 nm, Sr₂B₂O₅:Ce³⁺,Tb³⁺ phosphors exhibited blue emission corresponding to the f–d transition of Ce³⁺ ions and green emission bands corresponding to the f–f transition of Tb³⁺ ions, respectively. The Reflectance spectra of the Sr₂B₂O₅:Ce³⁺,Tb³⁺ phosphors are noted that combine with Ce³⁺ and Tb³⁺ ion absorptions. Effective energy transfer occurred from Ce³⁺ to Tb³⁺ in Sr₂B₂O₅ host due to the observed spectra overlap between the emission spectrum of Ce³⁺ ion and the excitation spectrum of Tb³⁺ ion. The energy transfer efficiency from Ce³⁺ ion to Tb³⁺ ion was also calculated to be 90%. The phosphor Sr₂B₂O₅:Ce³⁺,Tb³⁺ could be considered as one of double emission phosphor for n-UV excited white light emitting diodes.     

General optimization model for the energy planning of industries including renewable energy: A case study on oil sands

A multi‐period optimization model is developed for the energy procurement planning of industries including renewable energy. The model is developed with the objective of identifying the optimal set of energy supply technologies to satisfy a set of demands (e.g., power, heat, hydrogen, etc.) and emission targets at minimum cost. Time dependent parameters are incorporated in the model formulation, including demands, fuel prices, emission targets, carbon tax, lead time, etc. The model is applied to a case study based on the oil sands operations over the planning period 2015–2050. Various production alternatives were incorporated, including renewable, nuclear, conventional and gasification of alternative fuels. The results obtained indicated that the energy optimization model is a practical tool that can be utilized for identifying the key parameters that affect the operations of energy‐intensive industrial operations, and can further assist in the planning and scheduling of the energy for these industries. © 2016 American Institute of Chemical Engineers AIChE J, 63: 610–638, 2017     

Direct energy transfer to study the 3D structure of non-native proteins: AGH complex in molten globule state of apomyoglobin

The direct energy transfer technique was modified and appliedto probe the relative localization of apomyoglobin A-, G- andH-helixes, which are partly protected from deuterium exchangein the equilibrium molten globule state and in the molten globule-likekinetic intermediate. The non-radiative transfer of tryptophanelectronic energy to 3-nitrotyrosine was studied in differentconformational states of apomyoglobin (native, molten globule,unfolded) and interpreted in terms of average distances betweengroups of the protein chain. The experimental data show thatthe distance between the middle of A-helix and the N-terminusof G-helix as well as the distance between the middle of theA-helix and the C-terminus of the H-helix in the molten globulestate are close to those in the native state. This is a strongargument in favor of similarity of the overall architectureof the molten globule and native states.     

Insights into structure,local site symmetry,and energy transfer for regulating luminescent properties of SrLaLiTeO6: Dy/Eu and its application in wLEDs

A series of spectrally tunable Dy³⁺/Eu³⁺-coactivated double perovskites SrLaLiTeO₆ (SLLT) were synthesized via solid-state ceramic route under air condition. Considering differences of ionic radius and valences among the dopants and host cations, Dy³⁺/Eu³⁺ are all inclined to enter La site, though slight occupations in Sr site cannot be completely ruled out. Dy shows narrow band emissions in blue (B) to yellow (Y) region, which is stemmed from magnetic (⁴F_9/2 → ⁶H_15/2) and electric (⁴F_9/2 → ⁶H_13/2) dipole transitions, respectively. Eu³⁺ exhibits orange-red (O–R) emissions, with two dominant peaks located at ∼ 593 and 617 nm from magnetic (⁵D₀ → ⁷F₁) and electric (⁵D₀ → ⁷F₂) dipole transitions, which could be used as compensation for the red-emitting portion in pc-wLEDs via energy transfer (ET) from Dy to Eu to overcome the disadvantage of low excitation efficiency. The substitutional local site symmetry could be regularly modified along with severely impacting on Y/B and R/O ratios for Dy and Eu emission colors via simply modifying the doping contents, due to changes in bond lengths and Coulomb potentials from interconnected octahedrons [LiO₆] and [TeO₆] around the dopants. The fabricated pc-wLED via combining a commercial n-UV LED chip with the SLLT: Dy/Eu, exhibited splendid EL performance, with the CIE coordinate is calculated to be (0.3690, 0.3539), CCT of 3232 K, and CRI (R_a) of 86.5. Altogether, it manifests that the stable SLLT: Eu and SLLT: Dy/Eu are potentially good candidates for applications as red and white phosphors, respectively in indoor plant growth LED and pc-wLEDs.     

Electric permittivity of polyelectrolytes: 2. Effect of the concentration and ionic specificity

The dielectric behaviour of a polycondensate between L-lysine and 1,3-benzenedisulphonyl chloride (PLL) was studied at different concentrations and the effect of the nature of counterions was investigated. The effect of concentration on the dielectric increments and relaxation times are explained by the influence of polyion-polyion interactions on the dielectric parameters. In the presence of a bulky quaternary ammonium counterion (tetrabutylammonium), larger dielectric increments are found together with an increase in the high-frequency relaxation time.     

Preparation of CuMn2O4/Ti3C2 MXene composite electrodes for supercapacitors with high energy density and study on their charge transfer kinetics

In this study, we present a novel electrode material that combines Ti₃C₂ MXene and high-capacity CuMn₂O₄ to increase the energy density of supercapacitors, which are a popular choice for energy storage due to their high-performance potential. The electrode material was synthesized using the hydrothermal method with varying deposition times (3 h, 6 h and 9 h), and the resulting composite materials were characterized using advanced analytical techniques. The CuMn₂O₄/MXene composite electrode synthesized at 3h exhibited exceptional performance, with a specific capacitance of 628 mF/cm² at 4 mA/cm², due to the enhanced electrical conductivity and charge storage properties of CuMn₂O₄ and MXene sheets. We also uncovered an intricate charge transfer mechanism and storage kinetics of CuMn₂O₄/MXene composite on a nickel foam electrode, revealing a diffusion-controlled energy storage mechanism with fast mass transportation. To demonstrate practicality, we constructed an asymmetric coin cell supercapacitor device using CuMn₂O₄/MXene composite synthesized at 3h and activated carbon as the positive and negative electrodes, respectively. The device showed a specific capacitance of 496 mF/cm² at 6 mA/cm² with cyclic stability of 80% for up to 10,000 cycles, and a power density of 1.5 mW/cm² at a higher energy density of 0.073 mWh/cm². Our results demonstrate the potential to significantly advance the development of high-performance supercapacitors by combining Ti₃C₂ MXene and high-capacity oxides, refining the synthesis process, and exploring innovative electrode architectures.     

Converting trypsin to elastase: substitution of the S1 site and adjacent loops reconstitutes esterase specificity but not amidase activity

The conversion of trypsin into a protease with chymotrypsin-like activityand specificity required substitution of fifteen residues in the S1 siteand two surface loops with their chymotrypsin counterparts [Hedstrom,L.,Szilagyi,L. and Rutter,W.J. (1992) Science, 255, 1249- 1253]. Theseresidues may define a set of general structural determinants of specificityin the trypsin family. In order to test this hypothesis, we have attemptedto convert trypsin into a protease with specificity for substratescontaining small aliphatic residues by replacing the S1 site and thesesurface loops with the analogous residues of elastase. Five elastase-likemutant enzymes were constructed with various combinations of thesesubstitutions. Four mutant enzymes catalyze the hydrolysis ofMeOSuc-Ala-Ala-Pro-Ala-SBzl more efficiently than the hydrolysis ofSuc-Ala-Ala-Pro-Phe-SBzl. This observation indicates that the mutantenzymes have elastase-like esterase specificity. The best mutant,Tr-->E1-2, is a more specific esterase than elastase: the ratio of thevalues of kcat/Km for MeOSuc- Ala-Ala-Pro-Ala-SBzl andSuc-Ala-Ala-Pro-Phe-SBzl is greater than 160 for Tr-->E1-2 and 50 forelastase. However, the esterase activity of Tr- ->E1-2 is 300-fold lessthan elastase; in addition, Tr-->E1-2 has no measurable amidaseactivity. Thus these substitutions do not construct a protease withelastase-like activity. These experiments indicate that a unique structuralsolution is required for each different specificity. Previous worksuggested that instability of the S1 site is a major barrier to redesigningthe specificity of trypsin. This view is corroborated by preliminarystructural studies of Tr-->E1-2. One dimensional 1H NMR spectrum ofTr-->E1-2 suggests that the S1 site and the two surface loops of thismutant trypsin may be disordered.