5-Aminolevulinic acid and its derivatives: physical chemical properties and protoporphyrin IX formation in cultured cells

Protoporphyrin IX (PpIX) is used as a fluorescence marker and photosensitizing agent in photodynamic therapy (PDT). A temporary increase of PpIX in tissues can be obtained by administration of 5-aminolevulinic acid (ALA). Lipophilicity is one of the key parameters defining the bioavailability of a topically applied drug. In the present work, octanol-water partition coefficients of ALA and several of its esters have been determined to obtain a parameter related to their lipophilicity. The influence of parameters such as lipophilicity, concentration, time, and pH value on PpIX formation induced by ALA and its esters is then investigated in human cell lines originating from the lung and bladder. ALA esters are found to be more lipophilic than the free acid. The optimal concentration (c(opt), precursor concentration at which maximal PpIX accumulation is observed) is then measured for each precursor. Long-chained ALA esters are found to decrease the c(opt) value by up to two orders of magnitude as compared to ALA. The reduction of PpIX formation observed at higher concentrations than c(opt) is correlated to reduced cell viability as determined by measuring the mitochondrial activity. Under optimal conditions, the PpIX formation rate induced by the longer-chained esters is higher than that of ALA or the shorter-chained esters. A biphasic pH dependence on PpIX generation is observed for ALA and its derivatives. Maximal PpIX formation is measured under physiological conditions (pH 7.0-7.6), indicating that further enhancement of intracellular PpIX content may be achieved by adjusting the pharmaceutical formulation of ALA or its derivatives to these pH levels.     

The role of microscopy in understanding atherosclerotic lysosomal lipid metabolism.

Microscopy has played a critical role in first identifying and then defining the role of lysosomes in formation of atherosclerotic foam cells. We review the evidence implicating lysosomal lipid accumulation as a factor in the pathogenesis of atherosclerosis with reference to the role of microscopy. In addition, we explore mechanisms by which lysosomal lipid engorgement occurs. Low density lipoproteins which have become modified are the major source of lipid for foam cell formation. These altered lipoproteins are taken into the cell via receptor-mediated endocytosis and delivered to lysosomes. Under normal conditions, lipids from these lipoproteins are metabolized and do not accumulate in lysosomes. In the atherosclerotic foam cell, this normal metabolism is inhibited so that cholesterol and cholesteryl esters accumulate in lysosomes. Studies of cultured cells incubated with modified lipoproteins suggests this abnormal metabolism occurs in two steps. Initially, hydrolysis of lipoprotein cholesteryl esters occurs normally, but the resultant free cholesterol cannot exit the lysosome. Further lysosomal cholesterol accumulation inhibits hydrolysis, producing a mixture of cholesterol and cholesteryl esters within swollen lysosomes. Various lipoprotein modifications can produce this lysosomal engorgement in vitro and it remains to be seen which modifications are most important in vivo.     

A History of Fischer-Tropsch Wax Upgrading at BP—— from Catalyst Screening Studies to Full Scale Demonstration in Alaska

Conversion of Fischer-Tropsch wax into high quality synthetic crude or finished transportation fuels such as premium diesel has been studied over the past 15 years within BP. Catalyst screening and selection was carried out in dedicated micro-reactors and pilot plants, whose designs are critical to the performance selection. Variation in catalyst composition and defining the gas to oil feed ratios with the operating temperature are a few of the parameters studied. Product selection and maximizing diesel yield combined with stability (catalyst life) were the ultimate drivers. The selected catalyst was then tested under commercial conditions in a dedicated 300 barrel per day demonstration plant. The products were also tested in engines to assess their combustion characteristics.     

Organizational consequences of the hydrophobic interaction

If otherwise hydrophobic molecules also contain hydrophilic groups, they become known as “amphiphilic” and they are then subject to a potent organizational effect, which orients each molecule so as to satisfy as far as possible the thermodynamic requirements of both parts of the molecule. One consequence is the formation of monolayers of oil on water, which has been of great historical importance in physics and chemistry, leading to the first determinations of molecular size, symmetry and flexibility. The most important role of this kind of organizational force, however, is in biology. Here amphiphilic phospholipid molecules are organized into bilayers that are essential to the very existence of a living cell, defining the boundary between the inside of a cell and its environment. The formation of specific structures of proteins, too, is dominated by the hydrophobic interaction: in this case the need to fold the protein in such a way (intricately, with many twists and turns) as to minimize contact between hydrophobic groups and the surrounding aqueous medium. It is not an exaggeration to say that hydrophobic interactions are essential for all aspects of the chemistry of life as we know it.     

Relationship between acidification factors and methylene blue uptake by Ca-bentonite: optimisation and kinetic study

This investigation studied the uptake of methylene blue from wastewater by normal and treated bentonites to evaluate the effects of acidification factors on removal efficiency. Hydrochloric, sulphuric and nitric acids were blended in accordance with the response surface methodology to prepare acidic agents. The normal clay was then mixed with the prepared solutions after drying in a laboratory oven. The set-up provided controllable conditions for producing nano-porous powders for which the residence time and temperature were changed. The removal efficiency of the treated powders was assessed by defining an adsorption ratio and determining the optimal composition for acidic agent. Based on the statistical theory and experimental data, nitric acid is a suitable agent for manufacturing porous material to remove methylene blue from wastewater. In addition, the Brunauer-Emmett-Teller method, X-ray diffraction and Fourier transform infrared spectroscopy techniques were applied to identify the structural changes. The experimental data obtained from the batch tests were analysed by a new kinetic model which predicted the data variation with higher regression coefficients and lower relative errors. The proposed procedure can be an important tool in optimising the acidification conditions for manufacturing a nano-porous powder with maximal removal efficiency.     

甲醛与新制氢氧化铜反应实验的商榷及思考

利用SPSS21.0软件设计正交实验探讨甲醛与新制氢氧化铜反应的最佳条件,并在此条件下运用化学方法进行产物分析,得出主要产物为Cu,HCOONa,H2和H2O,副产物为Cu2O的结论。研究从明确实验条件、分析实验产物等方面提供了实验探究的样例。     

Quantum chemical calculation of the barrier for tunneling of hydrogen in hydrogen abstraction from methane by methyl

An adiabatic reaction path for hydrogen abstraction from methane by methyl is computed by quantum chemical methods and then symmetrized by properly defining the reaction coordinate. The theoretical barriers are then fitted with the barriers defined by the parabolic and Eckart functions. Rate constants for the hydrogen and deuterium-abstraction processes via tunneling at low temperatures are then computed.     

Sims characterization of La0.7Sr0.3MnO3 films for solid oxide fuel cell applications

Among solid oxides exploited to prepare efficient fuel cells, La(1-x)SrxMnO3 manganites have been widely studied and used as cathodes, because of their high conductivity at the working temperatures, good thermal stability and compatibility with other cell components. A fundamental goal in solid oxide fuel cells technology consists in lowering the normal operating temperatures, e.g. increasing the surface/volume ratio of electrodic materials, so as to enhance their catalytic performances. In this work, the preparation of high surface area La(1-x)SrxMnO3 (x approximately 0.3) films on silicon wafers by the nitrate-citrate Pechini process is described. The films were characterized by X-ray diffraction, Atomic Force Microscopy and Secondary Ion Mass Spectrometry. Good quality nanostructured perovskite-type films were obtained. SIMS methodology enabled to show the surface and in-depth coatings composition and residual contaminants. Moreover, it allowed defining the best synthesis conditions for complete in-depth decomposition of precursors and obtaining homogeneously thick coatings.     

Universality and individuality as complementary factors to optimize and reproduce cell populations

Irreversible thermodynamics allows us to formulate the law of mass action for a large number of reactions running off in open systems. By applying it to cell populations, these ensembles are supposed to be installed by defined increments. Stationary ensembles are then predicted to be optimized in the sense of thermodynamics of irreversible processes. General relations for describing the cell size distribution or the intracellular length distribution of proteins are deduced. During cell growth and multiplication, the cell size distributions change systematically in the course of time; yet, they are all reproduced by only adjusting the standard energy. This phenomenon is considered to originate with process-dependent constraints according to irreversible thermodynamics characterized by hidden variables. In agreement with the theoretical demands, all the different realizations belong to the same universal cell size distribution. Moreover, the universal stationary cell size distribution is classified by a single parameter, p. It is then of great importance that the stationary size distributions of cells of bacteria, yeast and human melanocytes all belong to the p=3 type, irrespective of the external conditions and of the individual chemical structure of the constituents. Universality also classifies the intracellular length distribution of proteins. The results discussed are enough to uncover as to how the genetically perfect production of the individual constituents and the thermodynamic optimization of the whole cell population are logistically coordinated.     

Physicochemical aspects of <Emphasis Type="Italic">Trichosporon cutaneum</Emphasis> CCY 30-5-10 adhesion and biofilm formation potential on cellophane

This paper focuses on the adhesion and biofilm formation potential of cellulolytic yeast Trichosporon cutaneum CCY 30-5-10 on solid cellophane from a novel perspective. First, physicochemical characterisation of the cells and carrier (cellophane) was performed to evaluate the effect of different culture media (complex vs mineral) on yeast cell adhesion. (Un)favourable adhesion conditions were predicted using the thermodynamic approach. Next, the ability of the cells to colonise the carrier under the above conditions was quantified and the biofilm structure was characterised using image analysis. The approaches described were found suitable to predict and experimentally verify favourable (cell-solid) adhesion, i.e. the hydrophobic and low electron-donor nature of cellophane together with hydrophobic cells (obtained when cultivated in a complex culture medium) were found to have a major impact in defining successful yeast adhesion with subsequent biofilm formation.     

The Role of Mechanical Properties and Structure of Type I Collagen Hydrogels on Colorectal Cancer Cell Migration

Mechanical interactions between cells and their microenvironment play an important role in determining cell fate, which is particularly relevant in metastasis, a process where cells invade tissue matrices with different mechanical properties. In vitro, type I collagen hydrogels have been commonly used for modeling the microenvironment due to its ubiquity in the human body. In this work, the combined influence of the stiffness of these hydrogels and their ultrastructure on the migration patterns of HCT-116 and HT-29 spheroids are analyzed. For this, six different types of pure type I collagen hydrogels by changing the collagen concentration and the gelation temperature are prepared. The stiffness of each sample is measured and its ultrastructure is characterized. Cell migration studies are then performed by seeding the spheroids in three different spatial conditions. It is shown that changes in the aforementioned parameters lead to differences in the mechanical stiffness of the matrices as well as the ultrastructure. These differences, in turn, lead to distinct cell migration patterns of HCT-116 and HT-29 spheroids in either of the spatial conditions tested. Based on these results, it is concluded that the stiffness and the ultrastructural organization of the matrix can actively modulate cell migration behavior in colorectal cancer spheroids.     

The surface chemistry of heterogeneous catalysis: mechanisms, selectivity, and active sites

The role of chemical kinetics in defining the requirements for the active sites of heterogeneous catalysts is discussed. A personal view is presented, with specific examples from our laboratory to illustrate the role of the chemical composition, structure, and electronic properties of specific surface sites in determining reaction activity and selectivity. Manipulation of catalytic behavior via the addition of chemical modifiers and by tuning of the reaction conditions is also introduced.     

The prediction of inorganic crystal framework structures using excluded regions within a genetic algorithm approach

We have developed a new technique, which is complementary to other procedures, that will have wide applicability for generating new feasible framework structures with defined microporous architectures from the knowledge of only the unit cell dimensions, constituent elements and by defining forbidden regions within the unit cell.     

Electrophoresis of biological cells: charge-regulation and multivalent counterions association model

The electrophoresis of a biological cell is analyzed theoretically. An entity, which is of amphoteric nature, is used to simulate its electrophoretic behavior. To reflect conditions of practical interest, we assume that the liquid phase contains mixed (a:b)+(c:b) electrolytes, where a and c are the valences of cations, and b is the valence of anions. We consider the case where the surface of a cell contains both bivalent acidic and monovalent basic functional groups, the dissociation/association of them yields fixed surface charge, and the multivalent cations in the liquid phase are allowed to combine with dissociated acidic functional groups, which has the effect of lowering the charge density on cell surface. The electrophoretic behaviors of a cell under various conditions are illustrated. The results obtained can be used to identify the types of functional groups that may be present on cell surface. On the other hand, if the surface functional groups involved in cell electrophoresis are known, then their density and the associated dissociation/association constants can be estimated from experimental data.     

Selection of surfactants for cell lysis in chemical cytometry to study protein-DNA interactions

Protein-DNA interactions play a defining role in many cellular processes. Studying such interactions at the single-cell level is important and challenging. Here we make the first step toward achieving this goal with chemical cytometry. Chemical cytometry utilizes capillary separation for detailed chemical analyses of single cells. The cell is injected into a capillary, lysed, and its components are analyzed by CE or capillary chromatography with highly sensitive detection. In order to apply chemical cytometry to studies of protein-DNA interactions, cell lysis must not destroy protein-DNA complexes. Surfactants represent the most practical means of cell lysis inside the capillary. This work aimed at finding surfactants and lysis conditions that do not destroy protein-DNA complexes. We studied three groups of surfactants--ionic, zwitterionic, and nonionic--with respect to their ability to lyse the cell membrane without significantly influencing the stability of protein-DNA complexes. Nonequilibrium CE of equilibrium mixtures with surfactants in the equilibrium mixtures and in the run buffer was used to measure the equilibrium constant, K(d), and rate constant, k(off), of protein-DNA complex dissociation. We found that nonionic surfactants worked best: they lyse the plasma membrane without significantly influencing K(d), k(off), or the EOF. This work creates the foundation for studies of protein-DNA interactions in single cells by chemical cytometry.     

A hybrid local/global optimal control algorithm for dissipative systems with time-dependent targets: formulation and application to relaxing adsorbates

Open-system quantum optimal control theory for optical control of the dynamics of a quantum system in contact with a dissipative bath is used here for explicitly time-dependent target operators, O(t). Global and local control strategies are combined in a novel algorithm by defining a set of time slices, into which the total control time is subdivided. The optimization then proceeds locally forward in time from subinterval to subinterval, while within each subinterval global control theory is used with iterative forward-backward propagation. The subintervals are connected by appropriate boundary conditions. In the present paper, all operators are represented in the basis of the eigenstates of the field-free system Hamiltonian. The algorithm is first applied to and its computational performance tested for a two-level system with energy and phase relaxation, and later extended to a many-level model. Model parameters are chosen to represent the IR pulse excitation of the adsorbate-surface stretch mode of vibrationally relaxing CO on a Cu(100) surface. Various time-dependent targets are formulated to achieve (i) population inversion, (ii) the creation of a wavepacket, and (iii) overtone excitation by "ladder climbing."     

Fabrication of the First Disposable Three‐dimensional Paper‐based Concentration Cell as Ammonia Sensor with a New Method for Paper Hydrophobization by Laser Patterned Parafilm®

A new, simple and low‐cost method for patterning hydrophobic barriers in porous support such as paper by Parafilm® has been introduced. This method is then used for electrochemical paper‐based ammonia sensor construction. Ammonia sensor is based on electrochemical concentration cell which ammonia reaction with electrolyte in halves cell caused in concentration gradient and therefore potential difference dependent on ammonia concentration. The effect of concentrations of the involved chemicals, time periods of the required processes, the presence of Faraday cage as well as the effects of different salts used in the salt bridge on the response of the sensor, were investigated in order to find the optimized conditions.     

Mammalian plasma membrane proteins as potential biomarkers and drug targets

Defining the plasma membrane proteome is crucial to understand the role of plasma membrane in fundamental biological processes. Change in membrane proteins is one of the first events that take place under pathological conditions, making plasma membrane proteins a likely source of potential disease biomarkers with prognostic or diagnostic potential. Membrane proteins are also potential targets for monoclonal antibodies and other drugs that block receptors or inhibit enzymes essential to the disease progress. Despite several advanced methods recently developed for the analysis of hydrophobic proteins and proteins with posttranslational modifications, integral membrane proteins are still under-represented in plasma membrane proteome. Recent advances in proteomic investigation of plasma membrane proteins, defining their roles as diagnostic and prognostic disease biomarkers and as target molecules in disease treatment, are presented.     

Physical-chemical aspects of protein corona: relevance to in vitro and in vivo biological impacts of nanoparticles

It is now clearly emerging that besides size and shape, the other primary defining element of nanoscale objects in biological media is their long-lived protein ("hard") corona. This corona may be expressed as a durable, stabilizing coating of the bare surface of nanoparticle (NP) monomers, or it may be reflected in different subpopulations of particle assemblies, each presenting a durable protein coating. Using the approach and concepts of physical chemistry, we relate studies on the composition of the protein corona at different plasma concentrations with structural data on the complexes both in situ and free from excess plasma. This enables a high degree of confidence in the meaning of the hard protein corona in a biological context. Here, we present the protein adsorption for two compositionally different NPs, namely sulfonated polystyrene and silica NPs. NP-protein complexes are characterized by differential centrifugal sedimentation, dynamic light scattering, and zeta-potential both in situ and once isolated from plasma as a function of the protein/NP surface area ratio. We then introduce a semiquantitative determination of their hard corona composition using one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrospray liquid chromatography mass spectrometry, which allows us to follow the total binding isotherms for the particles, identifying simultaneously the nature and amount of the most relevant proteins as a function of the plasma concentration. We find that the hard corona can evolve quite significantly as one passes from protein concentrations appropriate to in vitro cell studies to those present in in vivo studies, which has deep implications for in vitro-in vivo extrapolations and will require some consideration in the future.     

Overview of Popular Techniques of Raman Spectroscopy and Their Potential in the Study of Plant Tissues

Raman spectroscopy is one of the main analytical techniques used in optical metrology. It is a vibration, marker-free technique that provides insight into the structure and composition of tissues and cells at the molecular level. Raman spectroscopy is an outstanding material identification technique. It provides spatial information of vibrations from complex biological samples which renders it a very accurate tool for the analysis of highly complex plant tissues. Raman spectra can be used as a fingerprint tool for a very wide range of compounds. Raman spectroscopy enables all the polymers that build the cell walls of plants to be tracked simultaneously; it facilitates the analysis of both the molecular composition and the molecular structure of cell walls. Due to its high sensitivity to even minute structural changes, this method is used for comparative tests. The introduction of new and improved Raman techniques by scientists as well as the constant technological development of the apparatus has resulted in an increased importance of Raman spectroscopy in the discovery and defining of tissues and the processes taking place in them.