Dependence Of Exchange Rate Research Articles

PH and urea dependence of amide hydrogen-deuterium exchange rates in the beta-trefoil protein hisactophilin.

Amide hydrogen/deuterium exchange rates were measured as a function of pH and urea for 37 slowly exchanging amides in the beta-trefoil protein hisactophilin. The rank order of exchange rates is generally maintained under different solution conditions, and trends in the pH and urea dependence of exchange rates are correlated with the rank order of exchange rates. The observed trends are consistent with the expected behavior for exchange of different amides via global and/or local unfolding. Analysis of the pH dependence of exchange in terms of rate constants for structural opening and closing reveals a wide range of rates in different parts of the hisactophilin structure. The slowest exchanging amides have the slowest opening and closing rates. Many of the slowest exchanging amides are located in trefoil 2, but there are also some slow exchanging amides in trefoils 1 and 3. Slow exchangers tend to be near the interface between the beta-barrel and the beta-hairpin triplet portions of this single-domain structure. The pattern of exchange behaviour in hisactophilin is similar to that observed previously in interleukin-1 beta, indicating that exchange properties may be conserved among beta-trefoil proteins. Comparisons of opening and closing rates in hisactophilin with rates obtained for other proteins reveal clear trends for opening rates; however, trends in closing rates are less apparent, perhaps due to inaccuracies in the values used for intrinsic exchange rates in the data fitting. On the basis of the pH and urea dependence of exchange rates and optical measurements of stability and folding, EX2 is the main exchange mechanism in hisactophilin, but there is also evidence for varying levels of EX1 exchange at low and high pH and high urea concentrations. Equilibrium intermediates in which subglobal portions of structure are cooperatively disrupted are not apparent from analysis of the urea dependence of exchange rates. There is, however, a strong correlation between the Gibbs free energy of opening and the denaturant dependence of opening for all amides, which suggests exchange from a continuum of states with different levels of structure. Intermediates are not very prominent either in equilibrium exchange experiments or in quenched-flow kinetic studies; hence, hisactophilin may not form partially folded states as readily as IL-1 beta and other beta-trefoil proteins.

Spin exchange between transition metal complexes and nitroxyl radicals in nonaqueous media

New complexes of diaza- and tetraaza-containing crown ethers, viz., 1,10-diaza-18-crown-6 (1), 1,4,8,12-tetraazacyclopentadecane (2), 1,4,8,11-tetraazacyclotetradecane (3), and 1,4,8,11-tetraazacyclotetradecane 1,4,8,11-tetrachloride tetraacetic acid tetrahydrate (4), with the divalent copper and nickel ions and the Cl–, Br–, ClO4 –, NO3 –, and AcO– counterions were synthesized. The exchange interactions of these compounds and paramagnetic copper and nickel salts with the TEMPO radical in MeOH—CHCl3 binary mixtures of different compositions were studied. The plots of the linewidths of the hyperfine coupling components of TEMPO vs. concentration of the ions and temperature show that the frequency of diffusion collisions is the rate-limiting step for spin exchange (strong exchange regime). A strong dependence of the exchange rate constant (k ex) on the crown ether and counterion structure was found. The isotropic hyperfine coupling constants (a Cu) and g factors (g i ) were measured for the CuII complexes with the crown ethers. In the case of the crown ether complexes 1—3 with CuCl2, the a Cu constant decreases linearly with an increase in Δg i = g i – 2.0023 in the series 3 < 2 < 1, whereas k ex increases linearly in the same series with a decrease in the contact HFC on the CuII nucleus (K) and a decrease in covalence of bonding. For the complexes of 2 with CuII and different axial ligands (counterions), k ex increases in the series Cl– < ClO4 – ≤ AcO– ≤ Br–; < NO3 –. In the case of the complexes of 2 with NiCl2, k ex increases in the series 1 < 4 < 3 ≈ 2. For the CuII and NiII salts with the Cl–, ClO4 –, and NO3 – anions, the k ex values are almost independent of the anion nature. The correlation of the k ex values with the electron-spin parameters of the complexes is discussed.

Non-linear dependence in inter-war exchange rates: some further evidence

This paper reconsiders the time-series properties of inter-war pound-franc and pound-dollar exchange rate returns in the context of a smooth transition variant of the threshold autoregressive model. It is found that autoregressive structure in returns is largely confined to values in proximity with thresholds which are possibly associated with market intervention points or market sentiment. Under joint estimation in conjunction with GARCH models of time-varying conditional volatility, these models satisfactorily capture all non-linearity in the data, and in the case of pound-dollar returns provide out-of-sample forecasts superior to alternative linear and non-linear models previously considered in the literature.

An examination of nonlinear dependence in exchange rates, using recent methods from chaos theory

Interest in the relevance of nonlinear dynamics to finance and economics has spurred the evolution of new ways to analyze time series data. Tests for chaos, based on a metric approach which measures spatial correlations, led to the development of the correlation dimension test for chaos and the BDS test for nonlinearity. More recently, a topological method has been introduced into the scientific literature which employs a simple qualitative test for chaos that is adaptable to the characteristics of financial data. A quantitative version is also presented here. Conflicting evidence exists about the presence of chaotic behavior in exchange-rate data. The qualitative topological test does not support evidence of a chaotic generating mechanism in these series. The quantitative form finds nonlinear dependence and is a useful diagnostic to determine the adequacy of ARCH-type models for this nonlinear structure.

Long‐term dependence in exchange rates

The extent to which exchange rates of four major currencies against the Greek Drachma exhibit long‐term dependence is investigated using a R/S analysis testing framework. We show that both classic R/S analysis and the modified R/S statistic if enhanced by bootstrapping techniques can be proven very reliable tools to this end. Our findings support persistence and long‐term dependence with non‐periodic cycles for the Deutsche Mark and the French Franc series. In addition a noisy chaos explanation is favored over fractional Brownian motion. On the contrary, the US Dollar and British Pound were found to exhibit a much more random behavior and lack of any long‐term structure.

Dépendance de court et de long terme des rendements de taux de change

Short- and Long-Run Dependence of Exchange Rate Returns by Christelle Lecourt In this paper, we estimate an ARFIMA-GARCH model as introduced by Baillie, Bollerslev and Mikkelsen (1996) for the four leading daily exchange rate returns. Our main contribution is to take account of ARCH effects using a GARCH model and to consider the kurtosis in the series by opting for a Student distribution rather than a normal distribution. The results obtained show that most of the exchange rate return series have a poor long-run memory. The economic implications of these findings are considerable. Firstly, they should help improve forecasts of returns. Secondly, they imply that the efficient market (in the weak sense) hypothesis does not hold.

Impact of chemical stimuli and temperature on water transport and mobility in germinating rape seeds by pulsed 1H NMR spectroscopy

Pulsed 1H NMR in vivo difference spectroscopy and germination were combined to elucidate the effect of exogenously applied estriol or ethanol on water retention in fully hydrated rape seeds. The presence of estriol or ethanol in the imbibition medium resulted in a reduction of the photoreversible phytochrome. An approach to the assessment of cell membrane permeability related to the intracellular water exchange rate, using the bi-exponential feature in the water proton spin–lattice relaxation rate R1 and spin–spin relaxation rate R2, is presented. The intracellular water exchange rate increases approximately two- and three-fold in seeds pre-treated with estriol or ethanol solution in comparison with water imbibed seeds. The activation energy for the germination rate was 61±6, 42±4 and 37±4 kJ mol-1 and the transition temperature was 281±2, 286±2 and 284±2 K for seeds imbibed with water, estriol and ethanol solution, respectively. The temperature dependence of the intracellular water exchange rate showed comparable values of activation energy and transition temperatures. All the results support the hypothesis that the two effects, thermal activation and increase in the seed cell membrane permeability, combine during water transport into the cell and result in the germination of rape seeds imbibed with estriol or ethanol solution. © 1997 John Wiley & Sons, Ltd.

Impact of chemical stimuli and temperature on water transport and mobility in germinating rape seeds by pulsed1H NMR spectroscopy

Pulsed 1H NMR in vivo difference spectroscopy and germination were combined to elucidate the effect of exogenously applied estriol or ethanol on water retention in fully hydrated rape seeds. The presence of estriol or ethanol in the imbibition medium resulted in a reduction of the photoreversible phytochrome. An approach to the assessment of cell membrane permeability related to the intracellular water exchange rate, using the bi-exponential feature in the water proton spin–lattice relaxation rate R1 and spin–spin relaxation rate R2, is presented. The intracellular water exchange rate increases approximately two- and three-fold in seeds pre-treated with estriol or ethanol solution in comparison with water imbibed seeds. The activation energy for the germination rate was 61±6, 42±4 and 37±4 kJ mol-1 and the transition temperature was 281±2, 286±2 and 284±2 K for seeds imbibed with water, estriol and ethanol solution, respectively. The temperature dependence of the intracellular water exchange rate showed comparable values of activation energy and transition temperatures. All the results support the hypothesis that the two effects, thermal activation and increase in the seed cell membrane permeability, combine during water transport into the cell and result in the germination of rape seeds imbibed with estriol or ethanol solution. © 1997 John Wiley & Sons, Ltd.

Nonlinear dependence in British pound exchange rates

The Brock, Dechert and Scheinkman (1987) method is used to test for nonlinear dependence in daily rates of change of the exchange rate of the British pound relative to seven most heavily traded currencies against the pound during the period 2 January 1993 to 7 October 1996. The currencies are the US dollar, the Deutsche mark, the French franc, the Swiss franc, the Canadian dollar, the Japanese yen and the Italian lira. The results suggest that nonlinear dependence exists in all seven British pound exchange rates. Except for the US dollar, nonlinear dependence is due to nonlinearity in the variance and is captured by a GARCH(l,l)-t model. For the US dollar, nonlinear dependence is due to nonlinearity both in the mean and the variance and is captured by a GARCH-in-mean (GARCH-M) model.

Comparison of NH exchange and circular dichroism as techniques for measuring the parameters of the helix-coil transition in peptides.

Circular dichroism and NH exchange are compared directly as techniques for measuring helix content in peptides and the parameters of the helix-coil transition. To cover a broad range of helix contents, alanine-based peptides with chain lengths varying from 12 to 22 residues are examined over the temperature range from 0.6 to 26.9 degrees C in 1 M sodium chloride, 2H2O. Helix-coil transition theory independently fits both circular dichroism and exchange data, but the helix contents measured by exchange are larger than those measured by circular dichroism. The two techniques are brought into agreement by removing the assumption that the intrinsic chemical exchange rate in the helix is the same as the exchange rate measured for short unstructured model peptides. This modification allows the circular dichroism and NH exchange data to be described by the same set of helix parameters and indicates that the intrinsic exchange rate in the presence of helical structure is reduced approximately 17% relative to the rates measured in unstructured models. To test the possibility that this effect is electrostatic in origin, the sensitivity of the exchange reaction to ionic strength is determined. A substantial dependence of exchange rate on ionic strength is found, but the form of the dependence is complex. In studies of the exchange rates of native proteins, the exchange-competent form of the protein is assumed to exchange with the same rate constant as a blocked dipeptide with the identical amino acid sequences. Our result suggests that this assumption will be seriously in error in some cases because of charge effects in the protein.

Improving MR quantification of regional blood volume with intravascular T1 contrast agents: accuracy, precision, and water exchange.

The goal of this work was to develop a comprehensive understanding of the relationship between vascular proton exchange rates and the accuracy and precision of tissue blood volume estimates using intravascular T1 contrast agents. Using computer simulations, the effects of vascular proton exchange and experimental pulse sequence parameters on measurement accuracy were quantified. T1 and signal measurements made in a rat model implanted with R3230 mammary adenocarcinoma tumors demonstrated that the theoretical findings are biologically relevant; data demonstrated that over-simplified exchange models may result in measures of tumor, muscle, and liver blood volume fractions that depend on experimental parameters such as the vascular contrast concentration. As a solution to the measurement of blood volume in tissues with exchange that is unknown, methods that minimize exchange rate dependence were examined. Simulations that estimated both the accuracy and precision of such methods indicated that both the inversion recovery and the transverse-spoiled gradient echo methods using a "no-exchange" model provide the best trade-off between accuracy and precision.

An Examination of the Short‐Term and Long‐Term Behavior of Foreign Exchange Rates

AbstractThis study employs the heteroskedasticity‐robust variance ratio test and the modified rescaled range analysis to examine the short‐term and long‐term behavior of foreign exchange rates. The empirical results suggest that four of the five weekly nominal exchange rates examined exhibit short‐term dependence. Further, there is evidence of long‐term dependence in the nominal exchange rate series. The results also indicate that the real exchange rates generally exhibit short‐term independence, and the lack of strong evidence in favor of long‐term dependence in real exchange rates indicates that the purchasing power parity may not hold in the long run.

Dependence of the aboveground CO2 exchange rate on tree size in field-grown hinoki cypress (Chamaecyparis obtusa)

The CO2 exchange of the aboveground parts for five different-sized 17-year-old (as of 1991) hinoki cypress (Chamaecyparis obtusa) trees growing in the field was non-destructively measured over one year, using an open CO2 exchange system. The CO2 exchange of individual trees decreased with decreasing tree sizes, such as aboveground phytomass, leaf mass and leaf area. However, the CO2 exchange abruptly decreased near the smallest-suppressed sample tree. The size dependence was well described by a generalized power function. The annual gross photosynthesis of individual trees was proportional to the square root of leaf mass or leaf area. The dependence of CO2 exchange on annual phytomass increment was described by a simple power function with an exponent value less than unity, suggesting that CO2 exchange per unit of phytomass increment was lower in larger-sized trees than in smaller-sized trees. The mean photosynthetic activity of a tree, i.e., gross photosynthesis per unit of leaf area, slightly increased to its highest value with decreasing leaf area and then decreased abruptly near the smallest sample tree. The maximum value of mean photosynthetic activity was estimated to be 2.85 kg CO2 m−2 year−1 for a leaf area of 1.56 m2 tree−1. The ratio of mean photosynthetic activity to the maximum photosynthetic activity was the highest in an intermediate tree and decreased gradually toward larger-sized trees by ca. 60% and also decreased toward the smallest suppressed tree by ca. 35%.

The pH dependence of hydrogen-deuterium exchange in trp repressor: the exchange rate of amide protons in proteins reflects tertiary interactions, not only secondary structure.

The pH dependence of amide proton exchange rates have been measured for trp-repressor. One class of protons exchanges too fast to be measured in these experiments. Among the protons that have measurable hydrogen-deuterium exchange rates, two additional classes may be distinguished. The second class of protons are in elements of secondary structure that are mostly on the surface of the protein, and exchange linearly with increasing base concentration (log kex versus pH). The third class of amide protons is characterized by much higher protection against exchange at higher pH. These protons are located in the core of the protein, in helices B and C. The exchange rate in the core region does not increase linearly with pH, but rather goes through a minimum around pH 6. The mechanism of exchange for the slowly exchanging core protons is interpreted in terms of the two-process model of Hilton and Woodward (1979, Biochemistry 18:5834-5841), i.e., exchange through both a local mechanism that does not require unfolding of the protein, and a mechanism involving global unfolding of the protein. The increase in exchange rates at low pH is attributed to a partial unfolding of the repressor. It is concluded that the formation of secondary structure alone is insufficient to account for the high protection factors seen in the core of native proteins at higher pH, and that tertiary interactions are essential to stabilize the structure.

Redox-dependent dynamics of putidaredoxin characterized by amide proton exchange.

Multidimensional NMR methods were used to obtain 1H-15N correlations and 15N resonance assignments for amide and side-chain nitrogens of oxidized and reduced putidaredoxin (Pdx), the Fe2S2 ferredoxin, which acts as the physiological reductant of cytochrome P-450cam (CYP101). A model for the solution structure of oxidized Pdx has been determined recently using NMR methods (Pochapsky TC, Ye XM, Ratnaswamy G, Lyons TA, 1994, Biochemistry 33:6424-6432) and redox-dependent 1H NMR spectral features have been described (Pochapsky TC, Ratnaswamy G, Patera A, 1994, Biochemistry 33:6433-6441). 15N assignments were made with NOESY-(1H/15N) HMQC and TOCSY-(1H/15N) HSQC spectra obtained using samples of Pdx uniformly labeled with 15N. Local dynamics in both oxidation states of Pdx were then characterized by comparison of residue-specific amide proton exchange rates, which were measured by a combination of saturation transfer and H2O/D2O exchange methods at pH 6.4 and 7.4 (uncorrected for isotope effects). In general, where exchange rates for a given site exhibit significant oxidation-state dependence, the oxidized protein exchanges more rapidly than the reduced protein. The largest dependence of exchange rate upon oxidation state is found for residues near the metal center and in a region of compact structure that includes the loop-turn Val 74-Ser 82 and the C-terminal residues (Pro 102-Trp 106). The significance of these findings is discussed in light of the considerable dependence of the binding interaction between Pdx and CYP101 upon the oxidation state of Pdx.

Measurement and Analysis of Air Exchange Rates in a Greenhouse with Continuous Roof and Side Openings

The dresults of natural ventilation measurements carried out in a plastic greenhouse with continuous roof and side openings are presented. Both the static and turbulent pressure differences were taken into account. The results show a strong dependence of air exchange rate on wind velocity and total ventilator opening area as expected, but no important dependence on wind direction could be found for the conditions in which the experiments were conducted. Wind induced ventilation seems to become dominant when the wind speed exceeds about 1·8 m/s that is, the thermal buoyancy effect can be neglected. When the wind speed is lower than 1·8 m/s, although the thermal buoyancy effect is minor it cannot be neglected. Roof only and roof and side ventilator configurations are always more efficient than side only ventilator configuration. The best results for the calculated ventilation flux were obtained by a model that takes into account both thermal buoyancy and wind effects.

An examination of long-term dependence in black market exchange rates in eight Pacific-Basin countries

This study uses a modified rescaled range analysis to test for long-term dependence in foreign exchange rates. The test is performed on black market exchange rates of eight Pacific-Basin countries over the period of January 1974 to December 1988. Our results show that both monthly nominal and real exchange rates exhibit similar pattern; that is, they do not exhibit long-term dependence. Significant short-term serial correlations, however, are documented for most currencies. The results imply an exchange rate overshooting, and that purchasing power parity holds in the short run in these Pacific-Basin countries.

On the pH dependence of amide proton exchange rates in proteins

We have analyzed the pH dependencies of published amide proton exchange rates (kex) in three proteins: bovine pancreatic trypsin inhibitor (BPTI), bull seminal plasma proteinase inhibitor IIA (BUSI IIA), and calbindin D9K. The base-catalyzed exchange rate constants (kOH) of solvent exposed amides in BPTI are lower for residues with low peptide carbonyl exposure, showing that the environment around the carbonyl oxygen influences kOH. We also examined the possible importance of an exchange mechanism that involves formations of imidic acid intermediates along chains of hydrogen-bonded peptides in the three proteins. By invoking this "relayed imidic acid exchange mechanism," which should be essentially acid-catalyzed, we can explain the surprisingly high pHmin (the pH value at which kex reaches a minimum) found for the non-hydrogen-bonded amide protons in the beta-sheet in BPTI. The successive increase of pHmin along a chain of hydrogen-bonded peptides from the free amide to the free carbonyl, observed in BPTI, can be explained as an increasing contribution of the proposed mechanism in this direction of the chain. For BUSI IIA (pH 4-5) and calbindin D9K (pH 6-7) the majority of amide protons with negative pH dependence of kex are located in chains of hydrogen-bonded peptides; this situation is shown to be consistent with the proposed mechanism.

Sequence Dependence of Base-Pair Opening in a DNA Dodecamer Containing the CACA/GTGT Sequence Motif

Proton nuclear magnetic resonance spectroscopy is used to characterize the kinetics and energetics of base-pair opening in two self-complementary DNA dodecamer duplexes: [d(CGCACATGTGCG)]2 and [d(CGCAGATCTGCG)]2. The first dodecamer contains two symmetrical CACA/GTGT motifs; in the second dodecamer, each motif is interrupted by a change of the central C.G base pair to a G.C base pair. The opening rates and the equilibrium constants for formation of the open state of each base pair are obtained from the dependence of the imino proton exchange rates on the concentration of ammonia catalyst. The results indicate that the opening rates of the central three base pairs in the CACA/GTGT motif are 3-8-fold larger than the corresponding ones in the CAGA/GTCT sequence. The activation enthalpies and entropies, and the standard enthalpy and entropy changes for formation of the open state, are obtained from the temperature dependence of the opening rates and equilibrium constants, respectively. The results reveal that enthalpy/entropy compensation exists, for all base pairs in both dodecamers, in activation as well as in the equilibria between closed and open states. As a result, the opening rates and equilibrium constants for opening are maintained, in both dodecamers, within a relatively narrow range of values. Nevertheless, large sequence-induced variations are observed for the activation enthalpies and the standard enthalpy changes for opening. The A.T base pair located between the C.G base pairs in the CACA/GTGT motif has a negative enthalpy change for formation of the activated state during opening. This is the first case in which a negative activation enthalpy is observed for opening of a Watson-Crick base pair in DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Testing for non-linear dependence in inter-war exchange rates

Testing for Non-Linear Dependence in Inter-War Exchange Rates. — This paper tests weekly inter-war floating exchange rate data for the pound-dollar, pound-franc and pound-reichsmark for non-linearity. Initial tests reveal strong evidence of generic non-linearity in these series and indicate neglected non-linear structure in the residuals of linear representations. Attempts to model this structure using GARCH residual processes have only been partially successful. Thus, two parametric models of such non-linearity were estimated. Comparing the forecasts from these models shows the mean square forecast errors of linear-GARCH and bilinear models to be lower than those from linear forecasts for all series, and that SETAR model forecasts outperform all other models for the pound-dollar.