Showing papers by "University of Wisconsin-Madison published in 1985"

A Real-Time QRS Detection Algorithm

Abstract: We have developed a real-time algorithm for detection of the QRS complexes of ECG signals. It reliably recognizes QRS complexes based upon digital analyses of slope, amplitude, and width. A special digital bandpass filter reduces false detections caused by the various types of interference present in ECG signals. This filtering permits use of low thresholds, thereby increasing detection sensitivity. The algorithm automatically adjusts thresholds and parameters periodically to adapt to such ECG changes as QRS morphology and heart rate. For the standard 24 h MIT/BIH arrhythmia database, this algorithm correctly detects 99.3 percent of the QRS complexes.

The Optimal Degree of Commitment to an Intermediate Monetary Target

Abstract: Society can sometimes make itself better off by appointing a central banker who does not share the social objective function, but instead places "too large" a weight on inflation-rate stabilization relative to employment stabilization. Although having such an agent head the central bank reduces the time-consistent rate of inflation, it suboptimally raises the variance of employment when supply shocks are large. Using an envelope theorem, we show that the ideal agent places a large, but finite, weight on inflation. The analysis also provides a new framework for choosing among alternative intermediate monetary targets. I. INTRODUCTION It is now widely recognized that even if a country has a perfectly benevolent central bank (one that attempts to maximize the social welfare function), it may suffer from having an inflation rate which is systematically too high.' Suppose, for example, that a distortion (such as income taxation) causes the market rate of employment to be suboptimal. Then inflation can arise because wage setters rationally fear that the central bank will try to take advantage of short-term nominal rigidities to raise employment systematically. Only by setting high rates of wage inflation can wage setters discourage the central bank from trying to reduce the real wage below their target level. This paper considers some institutional responses to the timeconsistency problem described above. In particular, we examine the practice of appointing "conservatives" to head the central bank, or of giving the central bank concrete incentives to achieve an intermediate monetary target. Our analysis of intermediate monetary targeting is quite different from conventional analyses in which the central bank is rigidly constrained to follow a particular feedback rule. Indeed, an important conclusion is that it is not generally optimal to legally constrain the central bank to hit its intermediate target (or follow its rule) exactly, or to choose

Elections and Macroeconomic Policy Cycles

Abstract: There is an extensive empirical literature on political business cycles, but its theoretical foundations are grounded in pre-rational expectations macroeconomic theory. Here we show that electoral cycles in taxes, government spending and money growth can be modeled as an equilibrium signaling process. The cycle is driven by temporary information asymmetries which can arise if, for example, the government has more current information on its performance in providing for national defence. Incumbents cheat least when their private information is either extremely favourable or extremely unfavourable. An exogeneous increase in the incumbent party's popularity does not necessarily imply a damped policy cycle.

Structure of a human common cold virus and functional relationship to other picornaviruses

Abstract: We report the first atomic resolution structure of an animal virus, human rhinovirus 14. It is strikingly similar to known icosahedral plant RNA viruses. Four neutralizing immunogenic regions have been identified. These, and corresponding antigenic sequences of polio and foot-and-mouth disease viruses, reside on external protrusions. A large cleft on each icosahedral face is probably the host cell receptor binding site.

Stable replication of plasmids derived from Epstein-Barr virus in various mammalian cells

Abstract: Epstein-Barr virus (EBV) infects human B lymphocytes, transforming the infected cells into dividing blasts that can proliferate indefinitely. The viral genome of 172 kilobase pairs (kbp) is a plasmid in most transformed cells. We have identified a region of EBV DNA, termed oriP (nucleotides 7,333-9,109 of strain B95-8), which acts in cis to permit linked DNAs to replicate as plasmids in cells containing EBV DNA. We have postulated the existence of a trans-acting gene allowing oriP function. Here we report that this gene lies in a 2.6-kbp region of the viral genome (nucleotides 107, 567-110, 176) which encodes the EBNA-1 antigen. We show that circular DNAs containing oriP, the EBNA-1 gene and a selectable marker replicate autonomously in cells derived from at least four developmental lineages and from at least three species. We also find that the one-third of the EBNA-1 gene repetitive in sequence is not essential for the trans-acting function that EBNA-1 gives oriP.

The determinants of salesperson performance: A meta-analysis.

Abstract: The authors use meta-analysis techniques to investigate the evidence that has been gathered on the determinants of salespeople's performance. A search of the published and unpublished literature un...

Insertion of DNA sequences into the human chromosomal beta-globin locus by homologous recombination.

Abstract: A 'rescuable' plasmid containing globin gene sequences allowing recombination with homologous chromosomal sequences has enabled us to produce, score and clone mammalian cells with the plasmid integrated into the human beta-globin locus. The planned modification was achieved in about one per thousand transformed cells whether or not the target gene was expressed.

Current Control of VSI-PWM Inverters

Abstract: The inherent limitations of commanding voltages and currents in a three-phase load with an inverter are examined. An overview of several current controllers described in the literature is presented, and computer simulations are used to compare performance. A switching diagram is developed which reveals some of the operating characteristics of hysteresis controllers. For ramp comparison controllers, a frequency transfer function analysis is used to predict the line currents and provide some insight into the compensation required to reduce the current errors.

The Differential Effects of Exercised and Unexercised Power Sources in a Marketing Channel

Abstract: Though considerable research has been reported on the effects of coercive and noncoercive power sources in marketing channels, the particular effects of power sources that have been exercised, as o...

The heat shock response.

Abstract: The response of cells to a heat shock or other stresses is the activation of a small number of genes which were previously inactive or transcribed at low levels. This response has been observed in a wide variety of bacterial, plant, and animal species. Evidence is accumulating that at least some of the proteins found in diverse species are similar, indicating a conservation of the response and the proteins in evolution. In a number of organisms a strong positive correlation has been found between the presence of heat shock proteins and ability of the organism to withstand thermal stress. This review attempts to assess the available data concerning the homology of proteins in different species, the localization of the proteins in cells, and the relationship between heat shock proteins and thermoresistance.

Family Structure and the Reproduction of Poverty

Abstract: Recent analysts have argued that the female-headed family is responsible for the growth of an "underclass" in America. This study uses longitudinal data taken from the Michigan Panel Study of Income Dynamics to address the questions whether and why offspring in female-headed households are more likely to experience persistent poverty in adulthood. Four hypotheses regarding the effect of a father's absence are tested: the "no-effects" hypothesis, the "economic-deprivation" hypothesis, the "father-absence" hypothesis, and the "family-stress" hypothesis. Separate analyses are presented for blacks and whites. The findings indicate that growing up in a female-headed family increases the risk of poverty, but not because of father absence per se. Among whites, economic deprivation and the stress associated with recent family disruption account for nearly all the negative effects of family structure on offsprings' attainment, whereas among blacks the results are more mixed. During the past few years, researchers and policymakers alike have expressed a growing concern over the instability of the American family and the disorganization of community life. Concern for the family has focused on such issues as the increase in divorce, the rise in illegitimate births, and the subsequent growth of female-headed families. Evidence of broader disorganization is found in high levels of crime and drug abuse, in unemployment among large segments of minority youth, and more generally in what is characterized as the emergence of an "underclass" in America (Auletta 1981).

Common-sense models of illness: The example of hypertension.

Abstract: Our premise was that actions taken to reduce health risks are guided by the actor's subjective or common-sense constructions of the health threat. We hypothesized that illness threats are represented by their labels and symptoms (their identity), their causes, consequences, and duration. These attributes are represented at two levels: as concrete, immediately perceptible events and as abstract ideas. Both levels guide coping behavior. We interviewed 230 patients about hypertension, presumably an asymptomatic condition. When asked if they could monitor blood pressure changes, 46% of 50 nonhypertensive, clinic control cases said yes, as did 71% of 65 patients new to treatment, 92% of 50 patients in continuing treatment, and 94% of 65 re-entry patients, who had previously quit and returned to treatment. Patients in the continuing treatment group, who believed the treatment had beneficial effects upon their symptoms, reported complying with medication and were more likely to have their blood pressure controlled. Patients new to treatment were likely to drop out of treatment if: they had reported symptoms to the practitioner at the first treatment session, or they construed the disease and treatment to be acute. The data suggest that patients develop implicit models or beliefs about disease threats, which guide their treatment behavior, and that the initially most common model of high blood pressure is based on prior acute, symptomatic conditions.

The quantitative assessment of phylogenetic constraints in comparative analyses: sexual dimorphism in body weight among primates.

Abstract: We have presented a formal model for the quantitative analysis of phylogenetic and specific effects on the distribution of trait values among species. Total trait values are divided into phylogenetic values, inherited from an ancestral species, and specific values, the result of independent evolution. This allows a quantitative assessment of the strength of the phylogenetic inertia, or burden, displayed by a character in a lineage, so that questions concerning the relative importance of phylogenetic constraints in evolution can be answered. The separation of phylogenetic from specific effects proposed here also allows phylogenetic factors to be explicitly included in cross-species comparative analyses of adaptation. This solves a long-standing problem in evolutionary comparative studies. Only species' specific values can provide information concerning the independent evolution of characters in a set of related species. Therefore, only correlations among specific values for traits may be used as evidence for adaptation in cross-species comparative analyses. The phylogenetic autocorrelation model was applied to a comparative analysis of the determinants of sexual dimorphism in weight among 44 primate species. In addition to sexual dimorphism in weight, mating system, habitat, diet, and size (weight itself) were included in the analysis. All of the traits, except diet, were substantially influenced by phylogenetic inertia. The comparative analysis of the determinants of sexual dimorphism in weight indicates that 50% of the variation among primate species is due to phylogeny. Size, or scaling, could account for a total of 36% of the variance, making it almost as important as phylogeny in determining the level of dimorphism displayed by a species. Habitat, mating system, and diet follow, accounting for minor amounts of variation. Thus, in attempting to explain why a particular modern primate species is very dimorphic compared to other primates, we would say first because its ancestor was more dimorphic than average, second because it is a relatively large species, and third because it is terrestrial, polygynous, and folivorous.

Necessary and sufficient conditions for quadratic stabilizability of an uncertain system

Abstract: Consider an uncertain system (Σ) described by the equationx(t)=A(r(t))x(t)+B(s(t))u(t), wherex(t) ∈R n is the state,u(t) ∈R m is the control,r(t) ∈ ℛ ⊂R p represents the model parameter uncertainty, ands(t) ∈L ⊂R l represents the input connection parameter uncertainty. The matrix functionsA(·),B(·) are assumed to be continuous and the restraint sets ℛ,L are assumed to be compact. Within this framework, a notion of quadratic stabilizability is defined. It is important to note that this type of stabilization is robust in the following sense: The Lyapunov function and the control are constructed using only the bounds ℛ,L. Much of the previous literature has concentrated on a fundamental question: Under what conditions onA(·),B(·), ℛ,L can quadratic stabilizability be assured? In dealing with this question, previous authors have shown that, if (Σ) satisfies certain matching conditions, then quadratic stabilizability is indeed assured (e.g., Refs. 1–2). Given the fact that matching is only a sufficient condition for quadratic stabilizability, the objective here is to characterize the class of systems for which quadratic stabilizability can be guaranteed.

Milankovitch forcing of fluctuations in the level of tropical lakes from 18 to 0 kyr BP

Abstract: An atmospheric general-circulation model has been used to simulate the climates of January and July at 3,000-yr intervals. From 15 kyr BP onwards, the model simulates a strengthened monsoon circulation and increased precipitation in the Northern Hemisphere tropics, culminating at 9–6 kyr BP. The computed hydrological budgets were used to estimate the area of closed lakes between 8.9 and 26.6° N, giving, with minor exceptions, results in good agreement with geological evidence.

Pay satisfaction: its multidimensional nature and measurement.

Abstract: The present study was guided by the general hypothesis that pay satisfaction is multidimensional. The Pay Satisfaction Questionnaire (PSQ) was developed to assess five dimensions of satisfaction with pay (level, benefits, raises, structure, and administration). Results on two heterogeneous samples of employees provided support for the multidimensional hypothesis, although a four-dimensional solution (level, benefits, raises, structure/administration) provided better representation of the variance in the items studied. These four scales showed high internal consistency reliabilities. Comparison of the pay scales of the Job Descriptive Index and Minnesota Satisfaction Questionnaire with the PSQ dimensions suggested that these well-known scales primarily measure satisfaction with pay level. Implications of the findings for pay satisfaction research, both substantive and measurement oriented, are discussed.

Digestion of plant tissue for analysis by ICP emission spectroscopy

Abstract: A method of digesting plant tissue samples for multi‐element analysis by inductively‐coupled plasma (ICP) emission spectroscopy was developed which does not require the use of HclO4. A substitute oxidant, H2O2, eliminated the hazards associated with hot, concentrated HClO4. Optimal conditions for pre‐digestion and digestion were investigated. The procedure adopted consists of a pre‐digestion in concentrated HNO3 from room temperature to 60°C in 30 min followed by digestion at 90°C for 90 min with the addition of 30% H2O2 Analysis of NBS standard tissue samples by the proposed method gave results in good agreement with analysis following digestion in HNO3,‐HClO4 and with certified values, except for Fe.

Vitamin K-Dependent Carboxylase

Abstract: Vitamin K is an essential cofactor for a microsomal carboxylase that converts glutamyl residues in endogenous precursor proteins to y-carboxyglutamyl residues in completed proteins. The same microsomal preparations convert vitamin K to its 2,3-epoxide, and it has been suggested that these two reactions (carboxylation and epoxidation) are coupled. Glutathione peroxidase, which reduces hydrogen peroxide and organic hydroperoxides, inhibits both of these reactions in a preparation of microsomes solubilized by Triton X-100. Catalase has no effect. In the absence of vitamin K, and in the presence of NADPH, tert-butyl hydroperoxide acts as a weak vitamin K analog. At lower concentrations, tert-butyl hydroperoxide is an apparent competitive inhibitor of vitamin K for both the carboxylase and epoxidase reactions. These data are consistent with the hypothesis that both of these vitamin K-requiring reactions involve a common oxygenated intermediate, and that a hydroperoxide of the vitamin is the species involved. Vitamin K functions in the postribosomal modification of liver microsomal precursor proteins to form biologically active prothrombin, and the other vitamin K-dependent plasma clotting factors: VII, IX, and X (1, 2). The vitamin K-dependent modification of these precursors involves the carboxylation of specific glutamyl residues to form y-carboxyglutamyl residues in the completed proteins, and in vitro microsomal systems that carry out this vitamin K-dependent carboxylation have been developed (3-7). These systems, which have now been solubilized (8-13), have utilized the endogenous microsomal precursor protein(s) as a substrate for the carboxylase; more recently, synthetic peptides that are analogous to Glu-containing regions of the prothrombin precursor have been used as substrates (14, 15). This carboxylation reaction requires the reduced form of vitamin K, 02, and CO2 but appears to have no ATP, coenzyme A, or biotin requirement. The same microsomal preparations that catalyze the carboxylation also convert vitamin K to its 2,3-epoxide (16-18). It has been suggested (16) that the epoxidation reaction may be coupled to the carboxylation reaction, and the evidence that relates to this hypothesis has recently been reviewed (19). One possible mode of coupling of these two reactions would be through a common intermediate. This report presents evidence that is consistent with the hypothesis that a hydroperoxide of the vitamin is involved in both of these reactions, and suggests possible molecular roles for the vitamin in this unique carboxylase. MATERIALS AND METHODS Incubation Conditions. Microsomal pellets were prepared from 7to 10-day vitamin K-deficient rat livers as previously described (14). The microsome pellets were solubilized in SIK (0.25 M sucrose/0.025 M imidazole/0.5 M KC1, pH 7.2) buffer containing 1.5% (vol/vol) Triton X-100 and centrifuged at The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. ?1734 solely to indicate this fact. 54 Evidence for a hydroperoxide y of Wisconsin, Madison, Wisconsin 53706 105,000 X g for 60 min to remove insoluble material. Incubations consisted of 0.4 ml of this supernatant and 0.1 ml of SIK buffer containing NADPH, peptide substrate, and other compounds as described in the figure legends. Tert-butyl hydroperoxide (t-butyl-OOH) was added directly to the incubation mixtures. Vitamin K was reduced with sodium dithionite (4), and vitamin K hydroquinone was added to the incubations in ethanol. Radioactive CO2 was added as 20 jCi of NaH14CO3 per ml (59.3 mCi/mmol, Amersham/Searle) (1 Ci = 3.7 X 1010 becquerels). Incubations were carried out at 27?C for 30 min with shaking in 13 X 100 mm tubes sealed with Parafilm. Anaerobic incubations were flushed with N2 for 30 min before the "4CO2 and vitamin were added. Glucose oxidase (50 units/ml), glucose (7 mM), and catalase (50 units/ml) were also present in anaerobic incubations to ensure oxygen depletion (units are as defined by the supplier). Conversion of vitamin K to its 2,3-epoxide (epoxidation) was measured by incubation with [3H]vitamin K, extracting the incubation mixtures with 2 vol of 3:2 (vol/vol) isopropanol/ hexane, and analyzing the extracts by thin-layer chromatography as previously described (18). Measurement of Radioactivity. Incorporation of 14CO2 into protein was measured by using repetitive trichloracetic acid precipitations and washes as previously described (8), and carboxylation of Phe-Leu-Glu-Glu-Leu was determined (14) by measuring fixed CO2 in the trichloroacetic acid-soluble material.t One milliliter of 10% trichloracetic acid was added to a 0.2-ml aliquot of the incubation mixture. This was immediately mixed with a vortex stirrer and allowed to sit at least 15 min on ice. The precipitate was centrifuged, and excess 14C02 was removed from the supernatant by gassing with CO02 for 5 min. A 0.2-ml aliquot of the degassed supernatant was added to 4.3 ml of Aquasol and shaken, and radioactivity was determined in a liquid scintillation spectrometer with external standardization. Counting efficiency was 70%. Enzymes and Chemicals. Glutathione peroxidase was purified from rat liver according to the method of Nakamura et al. (20) to a specific activity of 73.3 units/mg (one unit = 1 jmol of H202 reduced per min at 25?C). A single band was obtained upon electrophoresis in nondenaturing 7% and 9% polyacrylamide gels. Glutathione reductase, catalase (C-100, twice reAbbreviations: t-butyl-OOH, tert-butyl hydroperoxide; GSH-Px, glutathione peroxidase. * To whom r print requests should be addressed. t Peptide carboxylase activity refers to the amount of vitamin Kdependent nonvolatile radioactivity present in a trichloroacetic acid supernatant after incubation in the presence of a peptide substrate and H"4CO-. Protein carboxylase activity refers to the vitamin K-dependent trichloroacetic acid-precipitable radioactivity in the same system. The endogenous protein substrates carboxylated include the prothrombin precursors (3, 8) and presumably precursors of other vita in K-dependent proteins. It has been previously shown (8, 14) that the rad oact vity fixed in both systems is present as 'y-carboxyglutamic acid.

Passive avoidance in syndromes of disinhibition: psychopathy and extraversion

Abstract: According to the physiological animal model proposed by Gorenstein and Newman (1980; see also Newman, Gorenstein, & Kelsey, 1983), psychopaths and extraverts may be characterized by a common psychological diathesis related to behavioral inhibition (see also Fowles, 1980; Gray, 1982). One aspect of this diathesis involves deficient passive avoidance learning, which has been central to explanations of "unsocialized" (e.g., Trasler, 1978) and antisocial behavior (e.g., Hare, 1970). Results from three experiments supported our prediction that psychopaths and extraverts would exhibit deficient passive avoidance relative to nonpsychopaths and introverts, respectively. In addition, the passive avoidance deficit was particularly evident in tasks that required subjects to inhibit a rewarded response in order to avoid punishment. The latter finding may be important for explaining the inconsistent results regarding passive avoidance learning in psychopaths (e.g., Chesno & Kilmann, 1975; Schmauk, 1970). Discussion of the results focuses on the importance of reward in mediating the passive avoidance deficit of "disinhibited" individuals and on the existence of an indirect relationship between psychopathy and extraversion: one that is consistent with the observed experimental parallels as well as with the more ambiguous evidence regarding a direct correlation between measures of the two syndromes.

Consensus sequence for Escherichia coli heat shock gene promoters

Abstract: We have identified promoters for the Escherichia coli heat shock operons dnaK and groE and the gene encoding heat shock protein C62.5. Transcription from each promoter is heat-inducible in vivo, and each is recognized in vitro by RNA polymerase containing sigma 32, the sigma factor encoded by rpoH (htpR) but not by RNA polymerase containing sigma 70. We compared the sequences of the heat shock promoters and propose a consensus promoter sequence, having T-N-t-C-N-C-c-C-T-T-G-A-A in the -35 region and C-C-C-C-A-T-t-T-a in the -10 region. These sequences differ from the consensus sequence recognized by holoenzyme containing sigma 70, the major sigma in E. coli. We suggest that the accumulated consensus sequences of promoters recognized by alternate forms of holoenzyme are compatible with a model in which sigma recognizes only the -10 region of the promoter.

Electron-Transfer Reactions Associated with Host-Guest Complexation. Oxidation of Ferrocenecarboxylic Acid in the Presence of β-Cyclodextrin

Abstract: L'etude est faite par voltammetrie cyclique en solution aqueuse a pH 9,2 dans laquelle le ferrocene est present sous forme d'anion ferrocenecarboxylate

Fine root turnover in forest ecosystems in relation to quantity and form of nitrogen availability: a comparison of two methods.

Abstract: Two methods of estimating fine root production and turnover are compared for 13 forest ecosystems exhibiting a wide range in form (NH4+ vs. NO3-) and quantity of available nitrogen. The two methods are by comparison of seasonal maxima and minima in biomess and by nitrogen budgeting. Both methods give similar results for stands with low rates of nitrification. The budgeting method predicts higher fine root turnover and productivity than the max-min method for systems with significant rates of nitrification.

Individual Differences in Autonomic Response: Conditioned Association or Conditioned Fear?

Abstract: Cluster analysis was used to define three groups of subjects whose conditioned heart rate response emphasized either acceleration, deceleration, or moderate deceleration. A subject pool (N = 148) was generated from four separate studies of differential classical conditioning in which colored slides served as conditioned stimuli (CSs) and the unconditioned stimulus (UCS) was aversive auditory noise. Both the statistically generated Accelerator and Decelerator groups responded with a significant late interval deceleration to CS+. However, only Accelerators also displayed a significant mid-interval heart rate increase to CS+. Conditioned electrodermal responses were significantly more resistant to extinction for Accelerators than for the other two cluster groups. Accelerators also differed from Decelerators in that their affective judgments of the slide stimuli became less positively valent and less dominant from pre- to post-conditioning, effects not found for Decelerators. Moderate Decelerators produced mixed results across the several psychophysiological and verbal measures of conditioning, resembling Accelerators in their verbal report change, and Decelerators in their rapid electrodermal extinction. It is suggested that cluster assignment may reflect subjects' pre-conditioning learning set. All successfully conditioned subjects appear to learn a relationship between stimuli such that the appearance of the CS+ prompts an anticipatory orienting response (late interval heart rate deceleration). Accelerators differ from the other two groups in that they also condition a defensive response which is associated with a change in emotional judgments of the stimuli and may represent covert preparation for avoidance. The relationships between defensive responding, avoidance, and the concept of fear are considered, and the problem of desynchrony in emotional change (i.e., the Moderate Decelerators) is addressed. Finally, parallels are drawn between results from classical conditioning and clinical studies of fear and phobia, and further suggestions are made for utilizing the conditioning paradigm in the study of emotion.

Response of satellite cells to focal skeletal muscle injury.

Abstract: The time course and pattern of the initiation of satellite cell mitoses was studied following a crush injury of the distal third of the 30-day-old rat extensor digitorum longus, a muscle in which myofibers run the entire length of the belly. Satellite cell mitotic activity was monitored using autoradiography after injection of 3H-thymidine. Satellite cell labeling rose above control values by 15 hours post injury at the injured site and by 20 hours in the middle third or adjacent undamaged portion of the muscle. Labeling decreased in the proximal third of the muscle, so that by 25 hours post injury, a gradient of labeling was established along the muscle length. Electron microscopy (EM) quantitation showed that the reduced labeling in the proximal third resulted from a reduction in satellite cell numbers. The results suggest that mitotic activity of satellite cells after localized injury occurs mainly at or near the site of injury, but that many of the dividing cells have migrated from undamaged areas distant from the lesion site.

Molecular structure of troponin C from chicken skeletal muscle at 3-angstrom resolution

Abstract: The x-ray structure of chicken skeletal muscle troponin C (TnC), the Ca2+-binding subunit of the troponin complex, shows that the protein is about 70 angstroms long with an unusual dumbbell shape. The carboxyl and amino domains are separated by a single long alpha helix of about nine turns. Only the two high-affinity Ca2+-Mg2+ sites of the COOH-domain are occupied by metal ions resulting in conformational differences between the COOH- and NH2-domains. These differences are probably important in the triggering of muscle contraction by TnC. Also the structure of TnC is relevant in understanding the function of other calcium-regulated proteins, in particular that of calmodulin because of its strong similarity in amino acid sequence.