UV Absorption Technique Research Articles

Folding Kinetics of G-Quadruplexes: Duplex Stem Loops Drive and Accelerate G-Quadruplex Folding.

The folding kinetics is an important parameter affecting the relevance of DNA and RNA G-quadruplex (G4) structures in biological processes. Previous studies of the G4 folding kinetics mainly depended on fast measurement techniques. In previously available examples of G4s with loops up to three residues, the folding kinetics spanning several orders of magnitude has been reported, ranging from milliseconds to over 100 s. It is difficult to systematically and fundamentally understand the effect of multiple parameters, especially the loop properties, on the G4 folding kinetics, as the G4 fold is often altered when the sequence is varied. In this study, judicious choices of multiple parameters allowed us to bring various systems into the measurable window of a simple UV absorption technique. Using a well-controlled parallel-stranded G4 fold, we were able to systematically investigate the effect of seven different parameters of the environment and loop properties (temperature, K+ concentration, ionic strength, co-solute, loop length, loop sequence, and loop structure) on the G4 folding kinetics. We found that structured loops can drive up the G4 folding: for a long loop, the fast folding of a stem loop can guide the G4 folding and accelerate its folding kinetics by several orders of magnitude compared to an unstructured loop counterpart.

Distribution of propofol in pig brain regions after bleeding and volume replacement with two distinct solutions

Results: The results obtained revealed that the system potassium ascorbate/ferric chloride induced the best yield for carbonyl generation, after 24h degradation time, compared with the other two hydroxyl radical generating systems. Both methods to quantify the protein carbonyls used the detection of the derivates at 360nm, but the capillary electrophoresis was more sensitive and required smaller amount of sample, comparedwith the UV absorption technique. Both methods were validated according to the EMEA/CHMP/EWP/192217/2009 guideline. Conclusions: Both techniques proved to be robust and versatile for the assessment of protein carbonyls in biological samples.

A Novel Lightweight Low-Power Dual-Beam Ozone Photometer Utilizing Solid-State Optoelectronics

Abstract Recent advances in semiconductor materials and fabrication techniques have allowed the development of light-emitting diodes (LEDs) with wavelengths extending down into the UV-C region (λ < 280 nm). A new ozone photometer has been developed utilizing these novel light sources. The application of solid-state technology to the proven dual-beam UV absorption technique has improved instrument performance while reducing power consumption and weight compared to existing instrumentation. The newly developed instrument is expected to have an accuracy of 1% at surface level pressure, a resolution better than 1 ppb, and measurement rates up to 1 Hz over the range of ozone mixing ratios encountered from the earth’s surface to the middle stratosphere. Size, weight, and power consumption have also been significantly reduced, with a mass of 3 kg and a power consumption of less than 5 W. Initial development is focused on an instrument suitable for measurements from autonomous platforms and in harsh environments; however, the technology is highly adaptable to other applications.

平板型高分子電解質ブラシ表面におけるフィブリノゲン捕捉挙動

We investigated human plasma fibrinogen (HPF) immobilization onto a planar sodium polystyrene sulfonate (NaPSS) brush in a protein aqueous solution. The saturated amount and time constant of the phenomenon were measured using time-resolved attenuated total reflection (ATR) UV absorption technique. The static and kinetic behavior were revealed to depend on the salt concentration in the protein solution. The results indicate that the immobilization is driven by the entropic effect and coulombic interaction, in contrast to previous reports for micellar PEB that the entropic effect is dominant. The immobilization mechanism identified in this work is independent of the molecular species and is applicable for any combination of protein and planar PEB with the same sign of charge in water, which is consistent with the nonspecific immobilization of proteins onto various PEB that has been reported to date.

Determination of Na and Al Ions in Semiconductor Cleaning Solution Using Capillary Electrophoresis

most common process chemical used in the manufacturing process is a standard cleaning (SC) solution, a mixture of ammonia and hydrogen peroxide in deionized water. Since the purity of the SC solution used in the process has been required to the level of sub-ppb range, accurate and reliable determination of ionic contaminants becomes increasingly difficult. In order to satisfy the requirement of impurity control, inductively coupled plasma-mass spectrometer (ICP-MS), graphite furnace atomic absorption spectrometer (GFAAS), and ion chromatography (IC) are currently the most common analytical instruments used in the process. 3 However, those instruments are not designed for on-line monitoring but rather for off-line analysis. Recently, separation and detection of various particles, such as cells and nanoparticles, with capillary electrophoresis (CE) was reported, although the application of CE has been mostly limited to organic or biological samples. 4-6 Capillary electrophoresis has been emerging as an alternative to ICPAES and AAS for trace metal analysis. In CE, some analytes such as inorganic cations and anions do not absorb at all or only very weakly absorb the light in the UV range. Therefore, an indirect UV absorption technique, in which the analyte displaces a mobile phase additive in the eluted band, has been used successfully in capillary electrophoresis. 7-13 The displacement causes a decrease in the absorption or fluorescence signal, because the concentration of the mobile-phase additive is lower in the eluted bands when compared with its steady-state concentration. Recently, separation and detection of various kinds of metal ions, including, alkali, alkaline earth, transition metals, and even lanthanide ions by CE in the presence of UV absorbing complexing agent were reported. 14-18 For semiconductor application, method development and applications of capillary electrophoresis for determination of cations in the highest purity grades of hydrogen peroxides that has been utilized widely in critical wafer processing steps were reported. 3 However, no article for the determination of trace metals in SC solution was reported so far. In this work, a labmade CE with a movable pinhole for optical adjustment was built and demonstrated for the determination of Na and Al ions in SC solution for semiconductor application.

Coagulation and carbonization processes in slightly sooting premixed flames

UV absorption spectra in the 200–400 nm range and transient thermocouple measurements are used tocharacterize the process of nanoparticle formation and their carbonization to soot particles in slightly sooting premixed flames of ethylene. The UV absorption technique allows a quantitative determination of the concentration of both soot and nanoparticles. In the examined flame, the total particulate is initially present as nanoparticles, but even in the sooting region, where the yellow luminosity is dominant, soot particles represent less than 50% of the total mass of particulate. This technique can be easily used for the determination of soot and nanoparticles at the exhaust of real combustion devices and in urban polluted areas. Time-resolved thermocouple measurements are used to follow the variation along the flame axis of the emissivity of the particulate deposited by thermophoresis on the thermocouple junction. Thesevalues are used for the evaluation of an apparent rate of carbonization, which has been compared with the coagulation rate of the particles evaluated by scattering and extinction measurements. Both processes, carbonization and coagulation, show a second-order kinetic with a constant of the order of 5×1012 cm3/s. This technique has shown to be a very simple method for detecting nanoparticles, which can be applied also in diffusion flames and other practical systems. In addition, it furnishes emissivity values, which might be useful for a more realistic assessment of the radiative heat transfer of slightly luminous flames.

Balloon-borne resonance fluorescence instrument for in-situ measurement of atomic oxygen: Simultaneous measurement with ozone at 38–44 km

A balloon-borne resonance fluorescence instrument for in-situ measurement of atomic oxygen (O(3P)) was developed and its performance was characterized based upon numerical simulations and laboratory tests. A simultaneous measurement of O(3P) and ozone (O3) in the upper stratosphere was carried out onboard a high altitude balloon launched from Sanriku (39°N, 142°E), Japan on 9 September 1997. O3 was measured on the same balloon by the solar UV absorption technique. The measured density ratios [O(3P)]/[O3] at altitudes 38–44 km were found to be consistent with the calculated within the experimental uncertainties, although a systematic discrepancy was found above 41 km. It was difficult to make a detailed discussion about this discrepancy due to the insufficient precision and accuracy.

In situ resonant ultraviolet absorption of nitric oxide at highpressure

Measurements of nitric oxide (NO) have been made in a flat premixedflame at pressures up to 30 atm using line-of-sight resonant ultravioletabsorption. Data are reported at equivalence ratios of 0.98 and 1.3 andpressures of 1, 5, 10, 20 and 30 atm. The performance of the in situ UVabsorption technique was assessed at these elevated pressures by comparing themeasured absorption with those predicted by a detailed theoretical spectroscopicmodel for NO. Prior to this experiment the resonant models had not been verifiedat pressures greater than two atmospheres. Agreement within 25% was foundbetween the measurements and predictions with only slight modification of theexisting model for NO to account for line centre shifting and pressurebroadening. Continuum interference of hot oxygen (O2) on the NO absorptionspectra was not significant in the interpretation of the data.

Ozone Generation by Positive and Negative Wire-to-Plate Streamer Discharges

A UV absorption technique is used to investigate the ozone generation after a positive or negative streamer discharge in air at atmospheric pressure. The discharge apparatus consists of a 45 cm long wire-to-plate configuration with an electrode gap distance of 2.5 cm. After either positive or negative streamer discharges, the highest ozone density occurs in an area just below the wire electrode. Towards the ground plate, the ozone density decreases rapidly. Positive streamer discharges produce about twice as much ozone density as negative streamer discharges with the same pulse duration.

Changes in surface ozone amount and its diurnal and seasonal patterns, from 1954–55 to 1991–93, measured at Ahmedabad (23 N), India

A comparative study of surface ozone observed at Ahmedabad during 1954–55 and 1991–93 periods has been made. The 1954–55 measurements were made at 0600, 1000, 1400, 1800, and 2100 hours (IST) by an electro‐chemical method, whereas 1991–93 measurements are made at every 15 minutes interval by an UV absorption technique. Higher ozone concentrations including larger amplitudes of diurnal and seasonal variations have been observed during 1991–93 as compared to the measurements made during 1954–55. The observed seasonal maximum during 1954–55 is in spring months whereas during 1991–93, it is in winter months. Increase in the concentration of ozone from 0600 hrs in the morning to 1400 hrs in the noon time is higher in summer and October–November months for both the periods and lowest during monsoon season. Furthermore, this change is higher during 1991–93 period as compared to 1954–55 suggesting higher levels of ozone precursors. The average ozone concentration increased from 14.7 ppbv during 1954–55 to 25.3 ppbv during 1991–93, resulting in a linear increase of 1.45% per year. The increase in background ozone concentrations, for 2100 and 0600 hrs during monsoon months when there is low photochemical ozone production even during day time, is 0.49% per year.

UV absorption spectra and kinetics for alkyl and alkyl peroxy radicals originating from di-tert-butyl ether

Alkyl, (CH 3) 3COC(CH 3) 2CH 2, and alkyl peroxy, (CH 3) 3COC(CH 3) 2CH 2O 2, radicals from di-tert-butyl ether (DTBE), have been studied in the gas phase at 296 K. A pulse radiolysis UV absorption technique was used to measure the spectra and kinetics. Absorption cross sections were quantified over the wavelength range 220–330 nm. At 240 nm, σ (CH 3) 3COC(CH 3) 2CH 2 = (3.6 ± 0.4) × 10 −18 cm 2 molecule −1 and at 260 nm, σ (CH 3) 3COC(CH 3) 2CH 2O 2 = (3.8 ± 0.3) × 10 −18 cm 2 molecule −1 have been obtained. The observed rate constants for the self-reaction of (CH 3) 3COC(CH 3) 2CH 2 and (CH 3) 3COC(CH 3) 2CH 2O 2 radicals were found to be (2.9 ± 0.2) × 10 −11 cm 3 molecule −1 s −1 and (2.7 ± 0.2) × 10 −12 cm 3 molecule −1 s −1, respectively. For the reaction of the alkyl radical with O 2 in 1 atm pressure of SF 6 a rate constant of (7.2 ± 1.1) × 10 −13 cm 3 molecule −1 s −1 was found. The rate constants for the reaction of the alkyl peroxy radicals with NO and NO 2 were determined to be (1.8 ± 0.2) × 10 −12 and (9.9 ± 1.3) × 10 −12 cm 3 molecule −1 s −1, respectively. As a part of the work the rate constants k(F + DTBE) and k(O + DTBE) were determined to be (2.6 ± 0.6) × 10 −10 and (4.0 ± 0.9) × 10 −12 cm 3 molecule −1 s −1, respectively.

Spectrokinetic study of SF5 and SF5O2 radicals and the reaction of SF5O2 with NO

AbstractUV spectra of SF5 and SF5O2 radicals in the gas phase at 295 K have been quantified using a pulse radiolysis UV absorption technique. The absorption spectrum of SF5 was quantified from 220 to 240 nm. The absorption cross section at 220 nm was (5.5 ± 1.7) × 10−19 cm2. When SF5 was produced in the presence of O2 an equilibrium between SF5, O2, and SF5O2 was established. The rate constant for the reaction of SF5 radicals with O2 was (8 ± 2) × 10−13 cm3 molecule−1 s−1. The decomposition rate constant for SF5O2 was (1.0 ± 0.5) × 105 s−1, giving an equilibrium constant of Keq = [SF5O2]/[SF5][O2] = (8.0 ± 4.5) × 10−18 cm3 molecule−1. The SF5O2 bond strength is (13.7 ± 2.0) kcal mol−1. The SF5O2 spectrum was broad with no fine structure and similar to the UV spectra of alkyl peroxy radicals. The absorption cross section at 230 nm was found to (3.7 ± 0.9) × 10−18 cm2. The rate constant of the reaction of SF5O2 with NO was measured to (1.1 ± 0.3) × 10−11 cm3 molecule−1 s−1 by monitoring the kinetics of NO2 formation at 400 nm. The rate constant for the reaction of F atoms with SF4 was measured by two relative methods to be (1.3 ± 0.3) × 10−11 cm3 molecule−1 s−1. © 1994 John Wiley & Sons, Inc.

Upper limits for the rate constants of the reactions of CF 3O 2 and CF 3O radicals with ozone at 295 K

Using the pulse radiolysis UV absorption technique and subsequent simulations of experimental absorption transients at 254 and 276 nm, upper limits of the rate constants for the reactions of CF 3O 2 and CF 3O radicals with ozone were determined at 295 K, CF 30 2+O 3→CF 3O+2O 2 (4), CF 3O+O 3→CF 3O 2+O 2 (5). The upper limits were derived as k 4<0.5×10 −14 cm 3 molecule −1 s −1, and k 5<1×10 −13 cm 3 molecule −1 s −1. Results are discussed in the context of the atmospheric chemistry and ozone depletion by hydrofluorocarbons.

Absolute rate constants for the reaction of CF 3O 2 and CF 3O radicals with NO at 295 K

Using a pulse radiolysis UV absorption technique and subsequent simulations of experimental NO 2 and FNO absorption transients, rate constants for reaction between CF 3O and CF 3O 2 radicals with NO were determined, CF 3O 2 + NO→CF 3O + NO 2 (3), CF 3O + NO→CF 2O + FNO (5). k 3 was derived to be (1.68±0.26) × 10 −11 cm 3 molecule −1 s −1, and k 5 = (5.2±2.7) × 10 −11 cm 3 molecule −1, s −1. Results are discussed in the context of the atmospheric chemistry of halocarbons.

Subfractions in uremic plasma ultrafiltrate inhibit calcitriol metabolism

Previous study from our laboratory has demonstrated that uremic plasma ultrafiltrate suppresses both the production rate (PR) and metabolic clearance rate (MCR) of calcitriol in normal rats. To characterize the the substances responsible for the suppression of the synthesis and degradation of calcitriol, we fractionated 20 ml uremic plasma ultrafiltrates into 13 fractions using high-performance liquid chromatography (HPLC) and studied the effect of each fraction on calcitriol metabolism. We measured the MCR and PR of calcitriol in normal rats after they were infused for 20 hours with each fraction dissolved in 20 ml normal saline. Using a UV absorption and fluorescence emission technique, several known uremic compounds were identified as individual peaks corresponding to the fractions. We found that fractions 4, and 6 to 13 markedly reduced the MCR of calcitriol. The patterns of the MCR suppression by the HPLC fractions suggest that there were at least two groups of chemically distinguishable compounds. Infusion of a solution containing all 13 fractions of the uremic ultrafiltrate also inhibited the calcitriol synthesis. One of the 13 fractions (fraction 4, containing uric acid, xanthine, and hypoxanthine) was further fractionated into eight subfractions. Infusion of subfractions 4 to 7 markedly reduced both the PR and MCR of calcitriol. We conclude that uremic plasma ultrafiltrate contains factors that inhibit calcitriol synthesis and degradation. These substances have molecular weight less than 2,000 Daltons.

Extended path length UV absorbance detector for capillary zone electrophoresis

AbstractA method of UV absorbance detection for use in capillaries using axial as opposed to transcolumn illumination is described in which laser‐induced fluorescence acts as a tool for determining, indirectly, the absorbance within a given length of the capillary. The length of the optical path can be chosen arbitrarily, regardless of the capillary diameter. The technique is demonstrated by means of capillary zone electrophoresis (CZE), in which path lengths of up to a few millimeters can be tolerated without serious loss of separation efficiency. Results for 50‐μm‐diameter capillaries show that optical densities consistent with an optical path of 3 mm can be obtained. This leads to a considerable increase in absorbance signal, compared with the usual transcolumn UV absorption technique. It is concluded that further exploitation of the technique requires the use of a more stable light source.

UV absorption study of the dissociation of SO2 and SO in shock waves

AbstractThe thermal decomposition of SO2 and of the primary dissociation product SO have been studied in shock waves by the uv absorption technique. The controversy about SO2 dissociation data from uv absorption signals was resolved and attributed to the extensive overlap of SO2 and SO uv absorption spectra. The derived rate coefficients are k1/[Ar] = 1015.6 exp(‐420 kJmol−1/RT) cm3mol−1 s−1 (temperature range 3000–5000 K) for SO2 dissociation, and k3/[Ar] = 1014.6 exp(‐448 kJmol−1/RT) cm3 mol−1 s−1 (temperature range 4000–6000 K) for SO dissociation. Anomalously high values of the apparent collision efficiencies βc in SO2 dissociation are attributed to marked contributions from excited electronic states.

Utilization of UV Spectrum in Identification of Tablets

Requests for tablet identification, one of the drug information services, compose as much as 32% of the total requests made to our drug information office. It is often difficult for hospital pharmacists to identify when no information is labelled on the tablet and on the package. In order to settle the difficulty, the contents of tablets were identified by the UV absorption technique, which proved more reliable than the conventional method. As the spectrophotometry is easy to operate and versatile to apply, the technique is one of the most practically useful methods of the tablet identification.

S2 Formation during the Pyrolysis of H2S in Shock Waves

Abstract The rate of S2 formation from shock-heated H2S was measured by means of the UV absorption technique in the temperature range of 2380–3000 K. At all the temperatures measured, the S2 absorption during the reaction could be represented by (S2)t=(S2)∞{1−exp(−kt)}, where: k=109.2exp(−72 kcal⁄RT)s−1. The mechanism of the S2 formation was proposed, and the value of the second-order rate constant, k1, for the primary reaction, H2S+M→SH+H+M, was estimated as follows: k 1=1013.1exp(−92 kcal⁄RT)1mol−1s−1. The effects of the addition of NO and O2 on the rate of S2 formation were also investigated. The results showed the validity of the proposed reaction mechanism.

Kinetics of O 2 dissociation and recombination

Shock tube investigations of relaxation processes in O2 and O2-Ar mixtures have been carried out for several years at our laboratory. Herewe briefly review the techniques utilized, the results obtained, and give more detailed comparisons with other work. Three experimental programs have been carried out employing the uv absorption technique to measure the O2 concentration. The first experiment dealt with the dissociation rate of O2 by Ar catalysts from 5000 to 18,000°K. It was found that there exists an incubation time (of the order of a vibrational relaxation time) before the O2 dissociates. When this data is used in conjunction with the subsequently obtained recombination data, a T−1/2 pre-exponential factor was clearly indicated for the rate constant expression which is kd=4.2(±14%)×10−8T−1/2 exp (−D/RT) cm6/particle2·sec. The second experiment measured the recombination rate of O atoms by Ar catalysts between 1500 and 3000°K. The excess O atoms were produced by shocking dilute O3-Ar mixtures. At 2000°K the measured recombination coefficient kr is about 0.7×10−34 cm6/particle2·sec. This study, with the previously mentioned dissociation work, showed that Keq=kd/kr. The third investigation involved the details of the shock front structure in O2 from Mach 4–21. Between Mach 4 and 10 translational and rotational processes occurred simultaneously within the shock front. Between Mach 10 and 14 vibrational relaxation moved up to and finally was swallowed by the “shock front.” Around Mach 16 the dissociation process started within the “shock front.” The shock tube kd results for Ar catalyst, when extrapolated to 300°K, compare well with recombination studies. But the high catalytic efficiencies for O and O2 found around 5000°K (Ar:O2:O≈1:18:50) are not apparent at 300°K. For O2 the extrapolated high temperature work is about 40 times that measured at 300°K, while that for O atoms is 100–800 times that reputed to be measured at 300°K, depending on how the extrapolation is made. Although there is some doubt as to whether the catalytic efficiency of the O atom has been correctly measured at 300°K, estimates of its value by reinterpretation of other work in the literature still fails to close this gap to better than a factor of 10. It is suggested that for the chemically-active catalyst O and O2 the temperature dependence changes markedly between 300°K and approximately 3000°K.