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PubMed1993

Assessment of protein rotational diffusion by 13C off-resonance rotating frame spin-lattice relaxation: effect of backbone and side-chain internal motion.

The 13C off-resonance rotating frame spin-lattice relaxation technique is applicable to the study of protein rotational diffusion behavior in a variety of experimental situations. The original formalism of James and co-workers (1978) (J. Am. Chem. Soc. Vol. 100, pp. 3590-3594) incorporated random isotropic reorientational motion of a rigid spherical rotor with no provision for backbone or side-chain carbonyl group internal motion. Here we demonstrate that the failure to include such internal motion may lead to erroneous rotational correlation time determinations for overall reorientational motion. The effect becomes severe for protein molecular masses in excess of 100 kD. Inclusion of both backbone and side-chain carbonyl carbon internal motion, using reasonable parameters derived from the literature [R. Levy and M. Karplus (1979), Chemical Physics Letters, Vol. 65, pp. 4-11; G. Careri, P. Fasella, and E. Gratton (1975), Critical Reviews in Biochemistry, Vol. 3, pp. 141-164; G. Lipari, A. Szabo, and R. LEvy (1982), Nature, Vol. 300, pp. 197-198], plus corrections for anisotropic tumbling [C. F. Morgan, T. Schleich, G. H. Caines, and D. Michael (1990), Biopolymers, Vol. 29, pp. 469-480] and microscopic viscosity [S. H. Koenig (1980), ACS Symposium Series, Vol. 127, pp. 157-176], leads to reliable values for the correlation time describing overall protein reorientation up to molecular masses of approximately 1000 kD.

Carbon Isotopes↗
PubMed2005

Determination of absolute configurations of chiral molecules using ab initio time-dependent Density Functional Theory calculations of optical rotation: how reliable are absolute configurations obtained for molecules with small rotations?

The absolute configuration (AC) of a chiral molecule can be determined via calculation of its specific rotation. Currently, the latter is most accurately carried out using the TDDFT/GIAO methodology. Here we examine the reliability of this methodology in determining ACs of molecules with small specific rotations. We report TDDFT/GIAO B3LYP/aug-cc-pVDZ//B3LYP/6-31G* calculations of the sodium D line specific rotations, [alpha]D, of 65 conformationally rigid chiral molecules whose experimental [alpha]D values are small (<100). The RMS deviations, sigma, of calculated and experimental [alpha]D values is 28.9. The distribution of deviations is approximately Gaussian, i.e., random. For eight molecules, more than 10% of the set, the sign of the predicted [alpha]D is incorrect. In determining an AC of a rigid molecule from [alpha]D with 95% confidence, the calculated [alpha]D value must lie within +/-2sigma of the experimental [alpha]D for one, but not both, of the possible ACs. For the 65 molecules of this study +/-2sigma is 57.8. For conformationally flexible molecules, the error bar is +/- >57.8.

Journal Article↗
PubMed1998

An Off-resonance Rotating Frame Relaxation Experiment for the Investigation of Macromolecular Dynamics Using Adiabatic Rotations

15N off-resonance rotating frame relaxation can be applied to the study of internal dynamics in proteins in the millisecond to microsecond regime. We show that the performance of existing methods can be improved by application of simultaneous amplitude and phase-modulated adiabatic RF pulses to align the nuclear spin magnetization with the off-resonance spin-lock field for all the spins under investigation. Application of this technique to the 269-residue serine protease PB92 allowed the measurement of 15N off-resonance rotating frame relaxation rates for all nonoverlapping residues in the protein, including the arginine side chains, encompassing a chemical shift range of 50 ppm. Simulations indicate that by use of the proposed adiabatic RF pulses rotating frame relaxation rates can be obtained for magnetization vectors aligned at arbitrary angles with the static field. Copyright 1998 Academic Press.

Journal Article↗
PubMed2001

Rotating frame analog of spin-locking and spin-lattice relaxation in the doubly rotating frame.

The present paper reports the achievement of the rotating-frame analog of spin-locking and its application to the precise measurements of the spin-lattice relaxation time T(1DR) in the doubly rotating frame. After the magnetization is aligned along the resonant RF field H(1), a pulse sequence of a low-frequency oscillating magnetic field at exact resonance is applied perpendicular to H(1). We have overcome several technical difficulties arising from the fact that the rotating-wave approximation is not valid for the low-frequency field. We have theoretically derived an expression of T(-1)(1DR) due to fluctuating magnetic dipole interactions in the weak collision case and found an important relation among the spin-lattice relaxation rates T(-1)(1), T(-1)(1rho), and T(-1)(1DR). This relation can be used to ascertain whether the relaxation is only due to the fluctuating magnetic dipole interactions between like spins. The experiment was carried out on (1)H nuclei in tetramethylammonium iodide (CH(3))(4)NI and the temperature dependence of T(-1)(1DR) was measured together with that of T(-1)(1) and T(-1)(1rho). The activation energies and the preexponential factors of Arrhenius expressions of the correlation times are newly determined.

Journal Article↗
PubMed1988

A simple method for determination of rotational correlation times and separation of rotational and polarity effects from EPR spectra of spin-labeled biomolecules in a wide correlation time range.

A method using nitroxide radical spin labels for determining both the isotropic rotational correlation time tau R and the environmental polarity of the label is described. By means of a least square fitting method, the values of an effective hyperfine tensor A' and of an effective g value tensor g' of randomly oriented spin labels are determined from X-band EPR spectra on the basis of an effective time-independent Hamiltonian. The traces of the tensors deliver the information about the environmental polarity of the label and are not dependent on the rotational correlation time tau R. A new averaging parameter S (tau R), calculated on the basis of the principal values of the tensor A', permits the evaluation of the rotational correlation time tau R in a very wide time range between 10(-10) and 10(-6) s. An application of this method to spin-labeled methemoglobin over a large temperature range and in environments of different polarity is discussed.

Electron Spin Resonance Spectroscopy↗
PubMed1999

Achieving visual object constancy across plane rotation and depth rotation.

Visual object constancy is the ability to recognise an object from its image despite variation in the image when the object is viewed from different angles. I describe research which probes the human visual system's ability to achieve object constancy across plane rotation and depth rotation. I focus on the ecologically important case of recognising familiar objects, although the recognition of novel objects is also discussed. Cognitive neuropsychological studies of patients with specific deficits in achieving object constancy are reviewed, in addition to studies which test neurally intact subjects. In certain cases, the recognition of invariant features allows objects to be recognised irrespective of the view depicted, particularly if small, distinctive sets of objects are presented repeatedly. In contrast, in most situations, recognition is sensitive to both the view in-plane and in-depth from which an object is depicted. This result suggests that multiple, view-specific, stored representations of familiar objects are accessed in everyday, entry-level visual recognition, or that transformations such as mental rotation or interpolation are used to transform between retinal images of objects and view-specific, stored representations.

Attention↗
PubMed2002

Second generation light-driven molecular motors. Unidirectional rotation controlled by a single stereogenic center with near-perfect photoequilibria and acceleration of the speed of rotation by structural modification.

Nine new molecular motors, consisting of a 2,3-dihydro-2-methylnaphtho[2,1-b]thiopyran or 2,3-dihydro-3-methylphenanthrene upper part and a (thio)xanthene, 10,10-dimethylanthracene, or dibenzocycloheptene lower part, connected by a central double bond, were synthesized. A single stereogenic center, bearing a methyl substituent, is present in each of the motors. MOPAC93-AM1 calculations, NMR studies, and X-ray analysis revealed that these compounds have stable isomers with pseudoaxial orientation of the methyl substituent and less-stable isomers with pseudoequatorial orientation of the methyl substituent. The photochemical and thermal isomerization processes of the motors were studied by NMR and CD spectroscopy. The new molecular motors all show two cis-trans isomerizations upon irradiation, each followed by a thermal helix inversion, resulting in a 360 degrees rotation around the central double bond of the upper part with respect to the lower part. The direction of rotation is controlled by a single stereogenic center created by the methyl substituent at the upper part. The speed of rotation, governed by the two thermal steps, was adjusted to a great extent by structural modifications, with half-lives for the thermal isomerization steps ranging from t(1/2)(theta) 233-0.67 h. The photochemical conversions of two new motors proceeded with near-perfect photoequilibria of 1:99.

Journal Article↗
PubMed1994

Perception of motion in depth from luminous rotating spirals: directional asymmetries during and after rotation.

Motion aftereffect (MAE) following spiral rotation is often asymmetrical: centrifugal MAE exceeds centripetal MAE. Pronounced MAE asymmetry has been reported for conditions--especially with a minimal background pattern--promoting perception of motion in depth. Such conditions are predicted to elicit motion asymmetry during adaptation. In the present study observers viewed luminous spirals monocularly in the dark; they timed, and scaled for convincingness, motion in depth during and after rotation. Motion in depth during rotation was often almost continuous, but recession was more convincing than was approach. Approaching MAE lasted longer and was more convincing than was receding MAE: the duration difference was more pronounced than has been found in other MAE studies, corroborating the link between MAE asymmetry and motion in depth. A possible line of explanation resides in comparing spiral motion in depth with real motion in depth of objects: in particular, the rapid visual change and collision with the observer that characterises real approach of an object is lacking in spiral approach. Interspecies differences for 'looming' and MAE are discussed.

Adult↗
PubMed2001

Distinction between space groups having principal rotation and screw axes, which are combined with twofold rotation axes, using the coherent convergent-beam electron diffraction method.

23 sets of space groups remain indistinguishable by the convergent-beam electron diffraction (CBED) method. Recently, Tsuda, Saitoh, Terauchi, Tanaka & Goodman [Acta Cryst. (2000), A56, 359-369] demonstrated that the coherent CBED method can distinguish two space-group pairs (I23, I2(1)3) and (I222, I2(1)2(1)2(1)) by observing the relative arrangements of 2-fold-rotation and 2(1)-screw axes. The other ten space-group sets, which are composed of principal rotation and screw axes and other 2-fold-rotation axes such as P321 and P3(1)21 (P3(2)21), are shown to be distinguishable using the coherent CBED method.

Journal Article↗
PubMed1980

Senior registrar rotations. A survey of rotational arrangements.

A questionnaire was circulated to assess the extent and nature of problems with senior registrar rotations. Proper notice of an impending move, suitable accommodation provided at the rotation hospital, and a clear indication of which hospitals are involved in the rotation should reduce the number of difficulties encountered.

Anesthesiology↗
PubMed2000

Rotating machinery dynamics simulation. I. Rigid systems with ball bearing nonlinearities and outer ring ovality under rotating unbalance excitation

The radial clearance in rolling bearing systems, required to compensate for dimensional changes associated with thermal expansion of the various parts during operation, may cause dimensional attrition and comprise bearing life, if unloaded operation occurs and balls skid [D. Childs and D. Moyer, ASME J. Eng. Gas Turb. Power 107, 152-159 (1985)]. Also, it can cause jumps in the response to unbalance excitation. These undesirable effects may be eliminated by introducing two or more loops into one of the bearing races so that at least two points of the ring circumference provide a positive zero clearance [D. Childs, Handbook of Rotordynamics, edited by F. Ehrich (McGraw-Hill, NY, 1992)]. The deviation of the outer ring with two loops, known as ovality, is one of the bearing distributed defects. Although this class of imperfections has received much work, none of the available studies has simulated the effect of the outer ring ovality on the dynamic behavior of rotating machinery under rotating unbalance with consideration of ball bearing nonlinearities, shaft elasticity, and speed of rotation. To fill this gap, the equations of motion of a rotor-ball bearing system are formulated using finite-elements (FE) discretization and Lagrange's equations. The analyses are specialized to a rigid-rotor system, by retaining the rigid body modes only in the FE solution. Samples of the results are presented in both time domain and frequency domain for a system with and without outer ring ovality. It is found that with ideal bearings (no ovality), the vibration spectrum is qualitatively and quantitatively the same in both the horizontal and vertical directions. When the ring ovality is introduced, however, the spectrum in both orthogonal planes is no longer similar. And magnitude of the bearing load has increased in the form of repeated random impacts, between balls and rings, in the horizontal direction (direction of maximum clearance) compared to a continuous contact along the vertical direction (direction of positive zero clearance). This underlines the importance of the vibration measuring probe's direction, with respect to the outer ring axes, to capture impact-induced vibrations. Moreover, when the harmonic excitation is increased for a system with ideal bearings, the spectral peaks above forcing frequency have shifted to a higher-frequency region, indicating some sort of a hard spring mechanism inherent in the system. Another observation, is that for the same external excitation, vibration amplitude at forcing frequency in the bearing force spectrum is the same for systems with or without outer ring ovality.

Journal Article↗
PubMed1984

Liver-spleen studies with the rotating gamma camera. I: Utility of the rotating display.

The clinical utility of a computer-generated dynamic cine display (rotating display) of the unprocessed projection images of the liver and spleen obtained with rotating gamma-camera tomography was prospectively compared with that of the standard multi-view static scintigram display. Two hundred cases were independently and blindly analyzed by three observers. Each study was coded from 1-5, indicating the certainty of normality or abnormality present. When abnormality was noted, the study was assessed for the presence of metastatic disease, inhomogeneous uptake, hepatosplenomegaly, and colloid distribution shift. ROC analysis was then performed on the initial coding for certainty of abnormality, and the causes for discrepancies were evaluated from the assessment of the type of abnormality present. No significant interdisplay differences could be demonstrated. In the small percentage of cases where interdisplay disagreement occurred, this was usually accompanied by marked interobserver variation and was most commonly due to differing assessment of organ size. It is concluded that the static and rotating display formats can be used interchangeably in the evaluation of technetium-99m-labeled sulfur colloid liver studies.

Data Display↗
PubMed2006

Polarization and image rotation induced by a rotating dielectric rod: an optical angular momentum interpretation.

When light is transmitted along the axis of a rotating glass rod, the polarization of the light is rotated through a small angle [Proc. R. Soc. London, Ser. A349, 423 (1976)]. Under the same conditions, we predict a rotation of the transmitted image by exactly the same angle. The treatment of the two effects in terms of light's spin and orbital angular momentum suggests that they share a common origin.

Journal Article↗
PubMed1983

Comparison of two dissolution apparatuses: rotating basket versus rotating flask.

The U.S.P./N.F. dissolution test (method I or rotating basket method) and the rotating flask technique (RESO-TEST dissolution method) were applied to four commercial prolonged release theophylline dosage forms. The dissolution data obtained were converted into dissolution efficiencies and submitted to a correlation analysis, the result of which demonstrates the equivalency of both methods with respect to the characterization of the dissolution behaviour of the dosage forms tested. It is suggested to consider replacement of the official dissolution technique, the shortcomings of which are well-known from the literature, by the rotating flask technique.

Capsules↗
PubMed2000

MR anatomy of the subcoracoid bursa and the association of subcoracoid effusion with tears of the anterior rotator cuff and the rotator interval.

OBJECTIVE: We describe the MR anatomy of the subcoracoid bursa and findings associated with subcoracoid effusion. CONCLUSION: Fluid in the subcoracoid space, revealed on MR imaging of the shoulder, may lie in the subcoracoid bursa or the subscapularis recess (both structures can be distinguished with MR imaging). In our patients, subcoracoid effusions were often associated with anterior rotator cuff tears, including tears of the rotator interval.

Adult↗
PubMed2003

Association of biceps tendon tears with rotator cuff abnormalities: degree of correlation with tears of the anterior and superior portions of the rotator cuff.

OBJECTIVE: This study was performed to examine the relationship and association of abnormalities seen in the long head of the biceps brachii tendon to abnormal findings in the rotator cuff. MATERIALS AND METHODS: One hundred eleven patients underwent MR imaging for shoulder pain followed by arthroscopic or open shoulder surgery from January 1997 to December 2000. Patients were identified by a retrospective search, and all consecutive patients having undergone both MR imaging and surgery were included in the patient cohort. Official MR imaging interpretations were compared with operative reports, and all findings were recorded. RESULTS: Twenty-three patients were identified with partial- or full-thickness tears of the long head of the biceps tendon. The sensitivity, specificity, and accuracy of unenhanced MR imaging of the shoulder for detecting these bicipital tears were 52%, 86%, and 79%, respectively. When a tear was present in the biceps tendon, the prevalence of supraspinatous, infraspinatus, and subscapularis tendon tears was 96.2%, 34.6%, and 47.1%, respectively. Patients with biceps tendon tears were significantly more likely to also have subscapularis tendon tears (p < 0.0001) and supraspinatous tendon tears (p < 0.008) than those patients who did not have biceps tendon tears. No significant relationship was found between the presence or absence of a biceps tendon tear and the presence or absence of a infraspinatus or teres minor tendon tear (p = 0.17). CONCLUSION: Tears of the long head of the biceps tendon have a statistically significant association with tears of the anterior and superior rotator cuff and are highly correlated with tears of the supraspinatous and subscapularis tendons. When tears of these tendons are detected, specific attention directed toward the long biceps tendon is warranted to characterize the status of this structure that provides additional stability to the shoulder joint.

Adolescent↗
PubMed1995

[Functional and anatomical results after surgical treatment of ruptures of the rotator cuff. 2: postoperative functional and anatomical evaluation of ruptures of the rotator cuff].

PURPOSE OF THE STUDY: The authors examined the anatomic condition and the function of the rotator cuff obtained after an average period of four years following surgical repair in a series of 100 full thickness rotator cuff tears. The aim was to assess the validity of Constant's scoring method and to analyse risk factors and the frequency of recurrent tears. MATERIAL AND METHODS: The series comprised 98 patients, 62 men and 36 women whose average age was 56 years. It included 69 tears of less than 2 cm in size (39 cases) or between 2 to 4 cm (3 cases) of the supra-spinatus, 22 tears of the supra- and infraspinatus measuring between 2 to 4 cm, and 9 massive tears. The tendon of the long head of the biceps was pathological in 1/3 of cases. All 98 patients were operated on by the same surgeon using the same repair technique, and all followed ambulatory rehabilitation along the same principles of self-rehabilitation applied pre operatively. In each patient function was assessed using Constant's scoring method, and the condition of the repaired cuff was determined by ultrasonography at the time of clinical follow-up. The average follow-up period was 4 years (2 to 6 years). RESULTS: Ultrasonography revealed intact cuffs in 65 per cent, thinned cuffs in 11 per cent and recurrent full thickness tears in 24 per cent of cases. The risk of recurrent tear increased with the extent of the tear to be repaired (57 per cent), in older patient (25 per cent) and with a higher level of post-surgical occupational use (18 per cent). A drop in the post-operative Constant score had a predictive value for a full thickness recurrent defect. DISCUSSION: Constant's scoring method appears to be a reliable, reproducible method for analysing functional results following surgical repair of full thickness cuff tears and to reflect the anatomic condition of the repaired cuff. At clinical follow-up, the anatomic condition of the cuff is more determinant of final functional results than initial tear size. CONCLUSIONS: Assessment of functional results must be complemented by anatomic examination using ultrasonography in order to specify the size of any possible recurrent defect and to detect thinning of the cuff which cannot be identified by Constant's score. Analysis of the risk factors for recurrent tear led the authors to question the necessity of repairing massive tears in older patients and pointed to the valuable advantages of reinforcing fragile cuffs during initial repair especially in very active patients.

Adult↗
PubMed1995

[Functional and anatomical results after surgical treatment of ruptures of the rotator cuff. 1: Preoperative functional and anatomical evaluation of ruptures of the rotator cuff].

PURPOSE OF THE STUDY: In a consecutive series of 98 patients presenting 100 full thickness cuff tears and managed by the same medico-surgical team, the authors studied the correlation between preoperative shoulder function values and the anatomic lesions found at surgery. Predictive factors of tear size were evaluated and any elements that were likely to improve preoperative function were determined so that patients could be best prepared for surgery. The validity of preoperative radiographic assessment of lesions was examined. MATERIAL AND METHODS: Prior to surgery, each patient was given the same rehabilitation program, the same arthrotomographic assessment of lesions and each was rated functionally using Constant's scoring method. Preoperative radiographic assessment of lesions showed supra-spinatus tears in 69 per cent, combined supraspinatus and infraspinatus tears in 22 per cent, and tears involving the supraspinatus, infraspinatus and subscapularis in 9 per cent. RESULTS: The preoperative Constant score averaged 46/100 points. The score was higher when patients had been prepared by preoperative rehabilitation to overcome stiffness. The optimum duration of rehabilitation was found to be 3 months (p < 0.05). Active range of motion was 90 per cent of normal in 84 per cent of cases. The patients in this series therefore underwent surgery more for continuing severe pain (25 per cent) and muscle weakness (86 per cent) than for reduced active motion. DISCUSSION: Examination of the correlations existing between an anatomic lesion and the preoperative rating of shoulder function shows that the Constant preoperative score provides a good prediction of the size of the tear to be repaired (p = 0.0063). The greater the tear size, the lower the preoperative Constant sore is. Active range of motion (especially in abduction and external rotation) and muscular strength are factors with the most predictive value contrary to pain and discomfort which are influenced by tear size. CONCLUSION: Preparing patients suffering full thickness cuff defects through preoperative rehabilitation to overcome stiffness provides the best conditions for surgery. Constant's functional scoring method gives a reproducible and reliable reflection of the anatomic rotator cuff lesion to be repaired. Its use for preoperative rating is useful for determining a reference value for function prior to surgery.

Adult↗