Fabrication of protein chips based on 3-aminopropyltriethoxysilane as a monolayer

Although 3-aminopropyltriethoxysilane (APTES) is widely adopted as a monolayer in biosensors, experimental silanization takes at least 1 h at high temperature. Therefore, the feasibility of the silanization with APTES in a short reaction time and at room temperature was investigated. The surface modification of glass slides using a self-assembled monolayer of APTES with a concentration of 10% was studied by immobilizing FITC. APTES was successfully immobilized on the glass slide. The effect of reaction temperature and time of silanization were investigated. Various silanization conditions of APTES were examined by contact angle measurement and fluorescence microscopy. The surface of glass patterns with a gold thin film as background was characterized by determining the fluorescent intensities following the immobilization of fluorescein isothiocyanate (FITC), protein A-FITC, antimouse IgG-FITC and sheep anti-bovine albumin-FITC. The normalized fluorescent intensity indicated that a short period (4 min) of silanization at 25°C suffices to form an APTES thin film by the immobilization of protein A on a glass surface. Such a condition does not require microheaters and temperature sensors in a microfluidic system, which will significantly reduce the manufacturing process, cost, and reaction time in the future.     

Vinyl polymerization by a cobalt complex

The rate of decomposition of the complex, sodium bis(diethanolamine)cobaltate octahydrate was studied at pH 7 and pH 1,6, respectively. This complex was found to initiate the vinyl polymerization (polymerization of acrylamide and methacrylamide) at pH 1,6 in aqueous medium. There was no polymerization at pH > 4. The dependences of the rate of polymerization on monomer concentration, initiator concentration, temperature, and pH were studied. The overall activation energy of the polymerization reaction was calculated. A kinetic reaction scheme is proposed on the basis of the experimental data.     

Synthesis and Characterization of Polyacrylamides in Inverse‐Emulsions with an Isoparaffinic Solvent

Inverse‐emulsion polymerizations of aqueous solutions of acrylamide (AM) in an isoparaffinic solvent were carried out using Span 80 as emulsifier. The conversions at the end of inverse‐emulsion polymerizations were investigated by HPLC methods. The conversion has been influenced by the initiator concentration, the monomer concentration and the reaction temperature. The molar masses were determined by viscosity measurements, size exclusion chromatography (SEC) and static light scattering. The influence of initiator concentration, monomer concentration and reaction temperature on the average molar mass of polyacrylamide (PAM) was studied.     

Calcium-deficient apatite synthesized by ammonia hydrolysis of dicalcium phosphate dihydrate: influence of temperature, time, and pressure

In this work, calcium-deficient apatites (CDA) were synthesized by ammonia hydrolysis reaction of dicalcium phosphate dihydrate (DCPD; CaHPO4 x 2 H2O) to obtain biphasic calcium phosphates (BCP) without any extraionic substitution. The influence of three parameters was studied: temperature of the reaction (70 and 100 degrees C), time of the reaction (4 and 18 h), and the pressure (open and closed system). Experiments were made according to a factorial design method (FDM) allowing optimization of the number of samples as well as statistical analysis of results. Moreover, the influence of temperature (until 200 degrees C) was investigated. The crystal size of CDA was determined according to the Scherrer's formula and from Rietveld refinements taking the CDA anisotropy into account. The last method seems to be a reliable method to determine crystallite sizes of CDA, since crystallite sizes of CDA along <00l> and directions were accessible. The results describe the hydroxyapatite % (HA%) in BCP by a first-order polynomial equation in the experimental area studied and the HA content was found to increase by raising time and temperature of the reaction. Moreover, the type of reaction system (open/closed vessel) appeared to have little influence on HA%.     

Use of a unique chemiluminescence spectrometer in a study of factors influencing granulocyte light emission.

Factors contributing to variability in chemiluminescence (CL) measurements of phagocytizing granulocytes were identified and controlled. Observed CL was decreased by light quenching caused by red blood cells, hemoglobin, phagocytizable particles, and granulocytes. Increases in CL were achieved by opsonization with heat labile and heat stable (antibody) serum factors, reaction temperatures in the range of 37-40 degrees C, and mixing. The effects of controlled temperature variation and mixing were studied with a chemiluminescence spectrometer uniquely designed for such studies. Features of this spectrometer which make it more suitable than the previously employed scintillation spectrometers for the observation of granulocyte and other chemiluminescent systems include; (1) the ability to measure CL immediately upon reaction initiation; (2) simplicity of photomultiplier tube exchange; and (3) built-in optical filter holders for spectral analysis.     

Temperature-sensitive ascending neurons in the spinal cord of pigeons

Ascending neuronal activity in the lateral funiculus of the spinal cord of pigeons (spinalized at about C4, recordings at about C6) has been studied with regard to effects of temperature changes with a thermode in the vertebral canal between Th4 and C8. 2. Both warm-sensitive (35) and cold-sensitive (14) neurons were found. According to the change in impulse frequency during steplike thermal stimuli, different reaction types could be distinguished. Twenty-four warm-sensitive and seven cold-sensitive units showed a proportional frequency change without any dynamic reaction. Three other warm-sensitive neurons had an additional dynamic reaction (excitatory overshoot during warming, inhibition during cooling). Five warm-sensitive and three cold-sensitive units showed no static sensitivity but responded with outstanding dynamic frequency changes during rising or falling temperature. The activity of some neurons stopped suddenly above (4) or below (3) a critical temperature, which was always near the normal spinal temperature (about 41 degrees C). Altogether the reaction to rapid temperature changes was consistently greatest near the normal body temperature. 3. The mean static sensitivity of 17 warm-sensitive units was + 4.2 plus or minus 1.3 imp./sec. degrees C (mean value and s. d.) and that of three cold-sensitive ones minus 2.3 plus or minus 0.3 imp./sec. degrees C in the range 35 degrees minus 45 degrees C (vertebral canal temperature). The temperature coefficient (Q10) which was calculated for the same neurons showed great variations with mean values of about 5 for both warm- and cold-sensitive units.     

Kinetics study of palm oil hydrolysis using immobilized lipase Candida rugosa in packed bed reactor

Continuous hydrolysis of palm oil triglyceride in organic solvent using immobilized Candida rugosa on the Amberlite MB-1 as a source of immobilized lipase was studied in packed bed reactor. The enzymatic kinetics of hydrolysis reaction was studied by changing the substrate concentration, reaction temperature and residence time(tau) in the reactor. At 55 degrees C, the optimum water concentration was found to be 15 % weight per volume of solution (%w/v). The Michaelis-Menten kinetic model was used to obtain the reaction parameters, Km(app) and V max(app). The activation energies were found to be quite low indicating that the lipase-catalyzed process is controlled by diffusion of substrates. The Michaelis-Menten kinetic model was found to be suitable at low water concentration 10-15 %w/v of solution. At higher water concentration, substrate inhibition model was used for data analysis. Reactor operation was found to play an important role in the palm oil hydrolysis kinetic.     

Study on the mechanism of 1-cyanoguanidine cure of epoxy resins using model compounds

The mechanism of the reaction of 2,3-epoxypropyl phenyl ether ( 2 ), as a model compound, with 1-cyanoguanidine ( 3 ), for which different pathways have been proposed, is investigated using HPLC and ¹H NMR spectroscopy. The effect of stoichiometric ratio, temperature and catalytic reagent was studied. It was found that, independent on the stoichiometric ratio, at low temperature, etherification and addition at the primary amino group takes place and reaction of the cyano group only to a low extend. At higher temperature, HPLC diagrams show different peaks indicating a different mechanism.     

Spinodal decomposition induced by cross-linking reaction in a binary polymer mixture

Phase separation of a binary polymer mixture of poly{styrene-co-[p-2,2,2-trifluoro-1-hydroxy-1-trifluoromethylethyl-α-methylstyrene]} (PS(OH)) and poly[(methyl methacrylate)-co-(glycidyl methacrylate)] (PMMA(G)) upon cross-linking reaction was studied using time-resolved light scattering (TRLS) and optical microscopy. The blends of PS(OH)/PMMA(G), in which PMMA(G) containing 1.4 mol-% epoxy groups can be selectively cross-linked with the multifunctional agent 4,4′-methylenebis(o-chloroaniline) (MOCA) and PS(OH) contains 1.8 mol-% of the strongly proton-donating group  C(CF₃)₂OH, exhibit a lower critical solution temperature (LCST). The cross-linking reaction was carried out for two compositions of PS(OH)/PMMA(G)/MOCA, 50/50/0.7 and 40/60/0.8 (w/w/w), at various temperatures located in the one-phase region between the coexistence curve and the glass transition temperature of the blends. TRLS investigation shows that the phase separation takes place via spinodal decomposition (SD) induced by the increase in the molecular weight of PMMA(G) during the cross-linking reaction. A modulated phase structure with the characteristic features of periodicity and dual connectivity of the phases was developed in this case. The dynamics of SD were investigated in terms of changes of the peak scattering vector q_m(t) as a function of time. They are dependent on the reaction temperature and composition. A scaling relation q_m(t) ∝︁ t^−af(x) describing the behavior of the evolution of phase separation upon reaction was supported by the experiments.     

Enzymatic elimination of hydrogen peroxide by a methemoglobin/L-Tyrosine system

We studied the peroxidase activity of ferrylhemoglobin radical (Hb(Fe(4+) = O*)) generated by the reaction of metHb (Hb(Fe(3+))) with hydrogen peroxide (H(2)O(2)). To clarify the behaviors of ferrylHb radical, it was isolated from the reaction mixture of metHb and H(2)O(2) by GPC at 4 degrees C. The radical species underwent rapid autoreduction to metHb at 37 degrees C accompanied with denaturation; however, it was stable for several minutes at 4 degrees C. In ESR measurements, the signal of the ferrylHb radical immediately disappeared in the presence of L-Tyrosine (L-Tyr), and simultaneously, the signal of the ferric heme increased. This suggested that the ferrylHb radical immediately converted to metHb by L-Tyr even at 4 degrees C. Furthermore, dimerized L-Tyr was detected in the reaction mixture. This showed that the ferrylHb radical was reduced to metHb by electron donation from L-Tyr. The enzymatic reaction using L-Tyr as the substrate resulted in the elimination of H(2)O(2) in this system.     

Kinetics of poly(propylene fumarate) synthesis by step polymerization of diethyl fumarate and propylene glycol using zinc chloride as a catalyst

Diethyl fumarate and propylene glycol were reacted in the presence of a zinc chloride catalyst to synthesize poly(propylene fumarate) (PPF) over a period of 12 hours. The kinetics of the transesterification polymerization at 130 degrees C, 150 degrees C, and 200 degrees C were determined by gel permeation chromatography (GPC) analysis. The initial rate of polymerization at each temperature was quantified by calculating the rate of change of the number average molecular weight (Mn). At 200 degrees C, gelation of the PPF occurred after 4 h. GPC analysis of the reaction showed that PPF synthesized at 150 degrees C had a higher final Mn of 4600 (+/- 190) and a higher weight average molecular weight of 10500 (+/- 760) than at 130 degrees C (n = 3). The chemical structure of the PPF was verified by NMR and FT-IR analysis. This study demonstrated that the maximum Mn of PPF by a transesterification reaction is limited due to gelation of PPF at high temperature.     

Synthesis of a New Phosphonated Dimethacrylate: Photocuring Kinetics in Homo‐ and Copolymerization,Determination of Thermal and Flame‐Retardant Properties

In this work, we describe the synthesis of a new dimethacrylate phosphonate monomer by condensation of methacryloyl chloride with a phosphonate diol resulting from a radical addition of allyldiethyl phosphonate with 3‐mercapto propane‐1,2‐diol. The photochemical polymerization of this new monomer was first studied as a function of reaction temperature. The optimal conversion of the photopolymerization was 63% at 70°C. This new monomer is less reactive than the commercial dimethacrylate polyether of Bisphenol A, that we have used for copolymerization. The mechanical and thermal properties of the final material were studied as a function of dimethacrylate phosphonate monomer content. The ultimate conversion slightly decreases (from 72 to 55%) and the glass transition temperature drops from 44 to –26°C when the phosphorus content increases. The addition of phosphorus leads to an improvement of the thermal and flame‐retardant properties, i. e. a significant decrease in the degradation rate (factor 4.5) and a high increase in the amount of residue that remained after combustion (15% for the 2.5% phosphorus copolymer). Moreover, the Limited Oxygen Index (LOI) is increased from 16.9 (0% P) to 21.5 (2.5% P).     

Grafting of a vinyl acetate/methyl acrylate mixture onto cellulose. Effect of temperature and nature of substrate

A mixture of vinyl acetate and methyl acrylate was grafted onto cellulose by using ceric ions as initiator. The influence of temperature, oxygen and of the nature of the polymeric substrate (mercerized cellulose and grafted cellulose) on the grafting parameters was studied. High temperatures favour homopolymerization more than grafting. Successive oxidation of cellulose by ceric ions suggests two types of reaction sites in cellulose. A gel effect occurs when high grafting yield is reached. Polymerization is inhibited by oxygen.     

Crosslinking and modification of dermal sheep collagen using 1, 4-butanediol diglycidyl ether.

Crosslinking of dermal sheep collagen (DSC) was accomplished using 1, 4-butanediol diglycidyl ether (BDDGE). At pH values > 8.0, epoxide groups of BDDGE will react with amine groups of collagen. The effects of BDDGE concentration, pH, time, and temperature were studied. Utilization of a 4-wt % BDDGE instead of 1-wt % resulted in a faster reaction. Whereas similar values of shrinkage temperature were obtained, fewer primary amine groups had reacted at a lower BDDGE concentration, which implies that the crosslinking reaction had a higher efficacy. An increase in pH from 8.5 to 10.5 resulted in a faster reaction but reduced crosslink efficacy. Furthermore, an increase in reaction temperature accelerated the reaction without changing the crosslink efficacy. Crosslinking under acidic conditions (pH < 6.0) evoked a reaction between epoxide groups and carboxylic acid groups of collagen. Additional studies showed that no oligomeric crosslinks could be formed. However, hydrolysis of the epoxide groups played a role in the crosslink mechanism especially under acidic reaction conditions. The macroscopic properties of these materials were dependent on the crosslinking method. Whereas a flexible and soft tissue was found if crosslinking was performed at pH < 6.0, a stiff sponge was obtained under alkaline conditions. Reaction of DSC with a monofunctional compound (glycidyl isopropyl ether) led to comparable trends in reaction rate and in similar macroscopical differences in materials as observed with BDDGE.     

An evaluation of mechanical property and microstructural development in HAP-Ca polycarboxylate biocomposites prepared by hot pressing

A hot-pressing technique was used to prepare composites anticipated to be biocompatible. Ca(4)(PO(4))(2)O (TetCP) was reacted with an acrylic-itaconic copolymer (CoP) in the absence of a solvent to form composites comprised of Ca(10)(PO(4))(6)(OH)(2') (hydroxyapatite, or HAp) and the Ca polyalkenoate salt. The effect of temperature, pressure, and hot-pressing time on the mechanical properties and microstructure of the composites were studied. Results showed that both tensile strength and elastic modulus increased when temperature and time were increased. When the compaction pressure was increased, these properties initially increased but decreased at high pressures. These variations in the mechanical properties were correlated with the microstructure of these composites. The mechanism of the reaction was also studied. Reaction starts when the copolymer is heated to above its T(g) permitting it to flow and react with the TetCP grains. The COOH groups on the polymer are neutralized by Ca(2+) ions liberated from the TetCP. At the end of reaction, a network of the Ca polyalkenoate salt is formed in which HAp crystals are embedded.     

Synthesis of poly(chalcone)s by polycondensation of aromatic dialdehydes with aromatic diacetyl compounds

Poly(chalcone)s were prepared by polycondensation of aromatic dialdehydes with aromatic diacetyl compounds in methanesulfonic acid (MSA) or phosphorus pentoxide/methanesulfonic acid (PPMA). Polycondensations proceed smoothly at room temperature and produced poly(chalcone)s with inherent viscosities up to 0,97 dL · g^?1. The reaction of acetophenone with aromatic aldehydes in MSA or PPMA was studied in detail to demonstrate the feasibility for polymer formation. Poly(chalcone)s are only soluble in concentrated sulfuric acid and methanesulfonic acid at room temperature. Thermogravimetry of poly(chalcone)s showed 10% weight loss around 380 and 420°C in air and under nitrogen, respectively.     

The covalent coupling of proteins to periodate-oxidized sephadex: a new approach to immunoadsorbent preparation.

Proteins were covalently coupled in good yield to periodate-oxidized Sephadex. The reaction was studied in detail with respect to Sephadex type, sodium m-periodate concentration, protein (albumin or immunoglobulin) concentration, time course, temperature dependence, and pH optimum. The complexes were stable and were used successfully for the immunoadsorption of sheep anti-rabbit immunoglobulin antibodies.     

Kinetics of poly(propylene fumarate) synthesis by step polymerization of diethyl fumarate and propylene glycol using zinc chloride as a catalyst

Diethyl fumarate and propylene glycol were reacted in the presence of a zinc chloride catalyst to synthesize poly(propylene fumarate) (PPF) over a period of 12 hours. The kinetics of the transesterification polymerization at 130°C, 150°C, and 200°C were determined by gel permeation chromatography (GPC) analysis. The initial rate of polymerization at each temperature was quantified by calculating the rate of change of the number average molecular weight (Mn). At 200°C, gelation of the PPF occurred after 4 h. GPC analysis of the reaction showed that PPF synthesized at 150°C had a higher final Mn of 4600 (±190) and a higher weight average molecular weight of 10 500 (±760) than at 130°C (n = 3). The chemical structure of the PPF was verified by NMR and FT-IR analysis. This study demonstrated that the maximum Mn of PPF by a transesterification reaction is limited due to gelation of PPF at high temperature.     

Reactivity of the thermoregulatory centers of animals in a state of amytal hypothermia

Summary The temperature reaction to the introduction of a pyrogenic agent (killed culture ofB. mesentericus) was studied in condition of sodium amytal sleep. The work was carried out on 3 intact dogs and 2 dogs in which 3 digtant receptors were removed. Hypothermia after introduction of this narcotic was prolonged, less pronounced and dissimilar to that of the intact dogs. Introduction of pyrogen decreased the hypothermia and brought about increase of the body temperature to the initial level and even higher. The relative degree of increase of the body temperature was 2 to 3 times higher than the rise of the temperature in the control group. The data which were obtained point to the decrease of the tone (hypothermia) of the thermoregulating centers during amytal sleep and their relatively increased excitation to the pyrogenic stimulation. The results of these experiments likewise, support the fact that the decrease of activity of the brain cortex is connected with a certain disinhibition of the subcortical thermoregulating centers.Submitted by Active Member of the AMN SSSR S. V. Anichkov     

γ-ray polymerization of mesogenic diacrylates in the crystalline,liquid crystalline and liquid state — a kinetic study

A kinetic study of the γ-ray polymerization of three mesogenic diacrylates, 4,4′-bis(3-acryloyloxypropoxy)biphenyl (DAPB), 4,4′-bis(6-acryloyloxyhexyloxy)biphenyl (DAHB) and 4,4′-bis(11-acryloyloxyundecyloxy)biphenyl (DAUB), is presented. All compounds were studied on their polymerizability in the crystalline state. It was found that they can be completely polymerized though the reaction rates are very different and increase with increasing length of the alkylene spacer unit. Up to moderate conversion, solid-state polymerization is comparable with that of acrylamide and follows a t² rate law. DAPB was chosen for a detailed kinetic study of the in-source and post-polymerization in the crystalline, liquid crystalline and liquid phase. In-source polymerization is complete in the various phases though reaction rates and curve shapes of dose vs. conversion curves are very different. Possible origins such as enhanced molecular diffusion at elevated temperatures are discussed. X-ray studies indicate that a well-ordered polymer can be obtained from polymerization in a smectic phase, while polymers obtained from a crystaline or melt phase are considerably less ordered. Post-polymerization was studied as a function of the radiation dose and the temperature of the subsequent annealing process. It was found that the limiting conversion increases with increasing radiation dose and temperature of the annealing process, but the polymerization is always incomplete. Even post-polymerization in the melt phase does not exceed 55 percent conversion. The post-polymerization behaviour is comparable with that of acrylamide and can be described by a linear relation between conversion and annealing time t.