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PubMed2001

Electrostatic stabilization of a thermophilic cold shock protein.

The cold shock protein Bc-Csp from the thermophile Bacillus caldolyticus differs from its mesophilic homolog Bs-CspB from Bacillus subtilis by 15.8 kJ mol(-1) in the Gibbs free energy of denaturation (DeltaG(D)). The two proteins vary in sequence at 12 positions but only two of them, Arg3 and Leu66 of Bc-Csp, which replace Glu3 and Glu66 of Bs-CspB, are responsible for the additional stability of Bc-Csp. These two positions are near the ends of the protein chain, but close to each other in the three-dimensional structure. The Glu3Arg exchange alone changed the stability by more than 11 kJ mol(-1). Here, we elucidated the molecular origins of the stability difference between the two proteins by a mutational analysis. Electrostatic contributions to stability were characterized by measuring the thermodynamic stabilities of many variants as a function of salt concentration. Double and triple mutant analyses indicate that the stabilization by the Glu3Arg exchange originates from three sources. Improved hydrophobic interactions of the aliphatic moiety of Arg3 contribute about 4 kJ mol(-1). Another 4 kJ mol(-1) is gained from the relief of a pairwise electrostatic repulsion between Glu3 and Glu66, as in the mesophilic protein, and 3 kJ mol(-1) originate from a general electrostatic stabilization by the positive charge of Arg3, which is not caused by a pairwise interaction. Mutations of all potential partners for an ion pair within a radius of 10 A around Arg3 had only marginal effects on stability. The Glu3-->Arg3 charge reversal thus optimizes ionic interactions at the protein surface by both local and global effects. However, it cannot convert the coulombic repulsion with another Glu residue into a corresponding attraction. Avoidance of unfavorable coulombic repulsions is probably a much simpler route to thermostability than the creation of stabilizing surface ion pairs, which can form only at the expense of conformational entropy.

Amino Acid Sequence↗
PubMed2000

An efficient neural network approach to dynamic robot motion planning.

In this paper, a biologically inspired neural network approach to real-time collision-free motion planning of mobile robots or robot manipulators in a nonstationary environment is proposed. Each neuron in the topologically organized neural network has only local connections, whose neural dynamics is characterized by a shunting equation. Thus the computational complexity linearly depends on the neural network size. The real-time robot motion is planned through the dynamic activity landscape of the neural network without any prior knowledge of the dynamic environment, without explicitly searching over the free workspace or the collision paths, and without any learning procedures. Therefore it is computationally efficient. The global stability of the neural network is guaranteed by qualitative analysis and the Lyapunov stability theory. The effectiveness and efficiency of the proposed approach are demonstrated through simulation studies.

Artificial Intelligence↗
PubMed2004

Interaural level difference processing in the lateral superior olive and the inferior colliculus.

Interaural level differences (ILDs) provide salient cues for localizing high-frequency sounds in space, and populations of neurons that are sensitive to ILDs are found at almost every synaptic level from brain stem to cortex. These cells are predominantly excited by stimulation of one ear and predominantly inhibited by stimulation of the other ear, such that the magnitude of their response is determined in large part by the intensities at the 2 ears. However, in many cases ILD sensitivity is also influenced by overall intensity, which challenges the idea of unambiguous ILD coding. We investigated whether ambiguity is reduced from one synaptic level to another for 2 centers in the so-called ILD processing pathway. We recorded from single cells in the free-tailed bat lateral superior olive (LSO), the first station where ILDs are coded, and the central nucleus of the inferior colliculus (ICC), which receives a strong projection from the LSO, as well as convergent projections from many other auditory centers. We assessed effects of overall intensity by comparing ILD functions generated with different fixed intensities to the excitatory ear. LSO cells were characterized by functions that shifted in a systematic manner with increasing intensity to the excitatory ear. In contrast, significantly more ICC cells had functions that were stable across overall sound intensity, indicating that hierarchical transformations increase stability. Furthermore, a population analysis based on proportion of active cells indicated that stability in the ICC was greatly enhanced when overall population activity was considered.

Acoustic Stimulation↗
PubMedDate not supplied

A resonance frequency analysis assessment of maxillary and mandibular immediately loaded implants.

PURPOSE: This study evaluated the stability of implants in 51 patients following a clinical protocol of immediate functional loading. The stability during the first 3 months following implant placement was assessed according to bone type, implant location, and patient gender. MATERIALS AND METHODS: Twenty-two male and 29 female patients were treated with 344 Brånemark System implants placed in edentulous bone or extraction sites and put into functional loading using the Teeth in a Day protocol. Each implant was tested for primary stability with resonance frequency analysis (RFA) at the time of implant placement, and RFA was performed at examinations 30, 60, and 90 days following surgery. RESULTS: The analysis was based on the 276 implants that were successfully measured using RFA at all postoperative intervals. The clinical implant survival rate was 98.5% for the total population. RFA showed a decrease in bone-implant stability in the first month after implant placement from 70.35 +/- 0.5 to 66.38 +/- 0.50, followed by increases in stability in the second and third months (68.01 +/- 0.50 and 68.82 +/- 0.49, respectively), suggesting a process of adaptive bone remodeling around the implant. In general, lower initial stabilities were seen in softer bone types, in the posterior portions of the jaw compared to anterior areas, and in the female population. DISCUSSION AND CONCLUSION: The results of this study suggest an immediate loading protocol should have an undisturbed period of healing for the first 2 months following implant placement. The determination of "predictor" stability levels for different clinical conditions were based on multiple splinted implants, allowing a larger surface area to withstand the distribution of the load. The most significant "predictor" values from a surgical and prosthodontic perspective are those determined in soft bone, in reduced bone, or in areas where lever arms are created as a result of long spans between the implants.

Adolescent↗
PubMed1998

The postural stability control and gait pattern of idiopathic scoliosis adolescents.

OBJECTIVE: The static postural equilibrium and gait patterns between idiopathic scoliotic (IS) patients and normal subjects were studied to verify the best method to identify the functional disability in IS patients. DESIGN: The static stability in six postures and gait patterns among normal subjects and IS patients were compared. BACKGROUND: Postural stability control and gait analysis are non-invasive methods to identify many diseases. However, the dysfunction of IS patients in postural stability control and gait pattern is not clear. The results of this research may lead to further understanding of the etiology of idiopathic scoliosis in the postural equilibrium influencing aspects. METHODS: Thirty IS patients and fifteen normal subjects were recruited for postural stability control test and gait analysis using the force plate and 3-D motion analysis system. RESULTS: The IS patients generally produced higher sway area, lateral sway, sagittal sway, and sway radius than normal subjects. The cadence is smaller in the IS patients, but the stance phase and stride phase are similar to normal subjects. CONCLUSIONS: The IS patients are poor in postural stability control but their gait pattern is similar to that of normal subjects. Standing with trunk at full flexion is the most effective position to identify the postural stability control of IS patient.

Journal Article↗
PubMed1998

Effects of formulation and process variables on the aggregation of freeze-dried interleukin-6 (IL-6) after lyophilization and on storage.

This study assessed the impact of residual moisture, Tg, and excipient physical state of different formulations on the "in-process" and shelf-life stability of freeze-dried interleukin-6 (IL-6). The effect of an annealing procedure was also evaluated. Characterization of the lyophilizates was done by Karl Fischer titration, differential scanning calorimetry (DSC), and x-ray measurements. Analysis of protein stability was carried out by size exclusion chromatography (SEC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and turbidity measurements. During freeze-drying, the most effective protection against aggregation was provided by completely amorphous formulations consisting of trehalose or sucrose either alone or in combination with glycine or mannitol. Other amorphous formulations like those of sucrose with lysine-HCl or dextran could not provide comparable stabilization. In lyophilizates containing a crystallized excipient such as glycine or mannitol, IL-6 suffered destabilization, which was less pronounced if an additional amorphous excipient was present. For the completely amorphous formulations, aggregation was prevented during a 9-month storage at 25 and 40 degrees C as long as the storage temperature did not exceed the Tg value of the lyophilizate, otherwise severe damage occurred. Formulations containing amorphous dextran or lysine-HCl could not effectively stabilize IL-6 even when stored below Tg. Annealing helped to improve cake robustness and appearance, but for lyophilizates containing an excipient crystallized by annealing an increase of IL-6 aggregation was observed despite a storage below Tg. Thus, the amorphous state of the excipients and a high Tg can be considered necessary conditions for preventing aggregation of freeze-dried IL-6. Whether the conditions are also sufficient depends on the choice of excipients. Destabilization can occur with some excipients despite their amorphous state as well as in the presence of crystallized excipients despite a storage below Tg. Compared to sucrose, trehalose is a more favorable excipient for protein lyophilization because it exhibits a higher Tg, possesses better stabilizing properties, and can reduce protein aggregation which may have been caused by annealing.

Dextrans↗
PubMedDate not supplied

Inherent stability of proximal first metatarsal osteotomies: a comparative analysis.

Proximal first metatarsal osteotomies have been criticized for their instability leading to the dorsal displacement of the first metatarsal head. The purpose of this study was to compare inherent stability of fixated proximal oblique wedge and crescentic first metatarsal osteotomies against simulated vertical ground reactive forces. The authors evaluated four groups of 10 models each with various proximal osteotomy and fixation configurations. Group I was a control group of bone models without osteotomies; group II had oblique closing wedge osteotomies with one 2.7-mm, fully threaded, cortical screw fixation; group III had oblique closing wedge osteotomies with two 2.7-mm, fully threaded, cortical screw fixation; and group IV had proximal crescentic osteotomies with one 4.0-mm, partially threaded, cancellous screw fixation. All 40 bone models were stressed with simulated vertical ground reactive forces. Maximum load to achieve catastrophic failure was higher in the crescentic group (67.7 N, SD 15.1 N, p < or = .005), but the energy required to displace the osteotomy during the stressing sequence was higher in the two-screw oblique closing wedge osteotomy (390.6 N.mm, SD 153.4 N.mm, p < or = .01). The single-screw oblique closing wedge osteotomies showed the least ability to resist simulated vertical ground reactive forces (39.6 N, SD 19.1 N, p < or = .005).

Biomechanical Phenomena↗
PubMed2003

Two stability-indicating UV spectrophotometric methods for the analysis of hydrolyzed tinidazole.

Two UV spectrophotometric methods have been validated for the analysis of hydrolyzed tinidazole solutions. The pH of the samples must be 5.00-7.00 for both methods. The multiwavelength method may be used for samples degraded at pH 6-12 if the amount of conserved 5-nitroimidazole species is at least 93 mol.% of the original; the amounts of tinidazole and its two known impurities may be determined simultaneously. The accuracy was within 100+/-8% and the repeatability of measurement was <or=4% at 0.03-0.33 mM, which was the measuring and calibration range. The LOD and LOQ were determined to be 0.003-0.012 mM and 0.0274 mM, respectively. The single-wavelength method may be used for samples degraded at pH 1-5, at least until approximately 50-60% of the original tinidazole has decomposed; only the amount of tinidazole can be determined. The solutions were measured at 318 nm, and quadratic fitting was used for the calibration. The mean accuracies varied between 98.0 and 101.8% and all RSDs were <or=1.7% for the precision at 0.041-0.15 mM, which was the measuring range. The calibration range was 0.049-0.12 mM. The LOD and LOQ were 0.25 and 0.75 microM, respectively. The two methods were shown to produce statistically different results by cross-validation. At pH 10.0, tinidazole was decomposed approximately 30 times faster than its 4-nitro isomer; 2-methyl-4(5)-nitroimidazole was stable during the study.

Antitrichomonal Agents↗
PubMed1991

Correlation of metabolic stability and altered quaternary structure of oncoprotein p53 with cell transformation.

The phosphoprotein p53 seems to be implicated in various processes connected with cell transformation and in particular with the regulation of cell cycle and probably DNA replication. In the present paper we have analyzed two sets of closely related cell lines expressing the same p53 which exhibited either a nontransformed or a transformed phenotype. These cell lines were used to study biochemical properties of the p53 protein which might be correlated with cell transformation. We found a positive correlation among an elevated stability of p53, the formation of high-molecular-weight forms of p53, and the transformed phenotype of the corresponding cell lines. Furthermore, these data indicate that self-aggregation prevents p53 from rapid degradation. By a comparative analysis of the stability and oligomerization properties of mutant p53 and wild-type p53, we could demonstrate that elevated stability and self-aggregation of p53 are correlated with the transformed phenotype of the cells and independent of a particular mutation in the p53 gene.

Animals↗
PubMed2007

Comparison of the effects of bilateral posterior dynamic and rigid fixation devices on the loads in the lumbar spine: a finite element analysis.

A bilateral dynamic stabilization device is assumed to alter favorable the movement and load transmission of a spinal segment without the intention of fusion of that segment. Little is known about the effect of a posterior dynamic fixation device on the mechanical behavior of the lumbar spine. Muscle forces were disregarded in the few biomechanical studies published. The aim of this study was to determine how the spinal loads are affected by a bilateral posterior dynamic implant compared to a rigid fixator which does not claim to maintain mobility. A paired monosegmental posterior dynamic implant was inserted at level L3/L4 in a validated finite element model of the lumbar spine. Both a healthy and a slightly degenerated disc were assumed at implant level. Distraction of the bridged segment was also simulated. For comparison, a monosegmental rigid fixation device as well as the effect of implant stiffness on intersegmental rotation were studied. The model was loaded with the upper body weight and muscle forces to simulate the four loading cases standing, 30 degrees flexion, 20 degrees extension, and 10 degrees axial rotation. Intersegmental rotations, intradiscal pressure and facet joint forces were calculated at implant level and at the adjacent level above the implant. Implant forces were also determined. Compared to an intact spine, a dynamic implant reduces intersegmental rotation at implant level, decreases intradiscal pressure in a healthy disc for extension and standing, and decreases facet joint forces at implant level. With a rigid implant, these effects are more pronounced. With a slightly degenerated disc intersegmental rotation at implant level is mildly increased for extension and axial rotation and intradiscal pressure is strongly reduced for extension. After distraction, intradiscal pressure values are markedly reduced only for the rigid implant. At the adjacent level L2/L3, a posterior implant has only a minor effect on intradiscal pressure. However, it increases facet joint forces at this level for axial rotation and extension. Posterior implants are mostly loaded in compression. Forces in the implant are generally higher in a rigid fixator than in a dynamic implant. Distraction strongly increases both axial and shear forces in the implant. A stiffness of the implant greater than 1,000 N/mm has only a minor effect on intersegmental rotation. The mechanical effects of a dynamic implant are similar to those of a rigid fixation device, except after distraction, when intradiscal pressure is considerably lower for rigid than for dynamic implants. Thus, the results of this study demonstrate that a dynamic implant does not necessarily reduce axial spinal loads compared to an un-instrumented spine.

Biomechanical Phenomena↗
PubMed2004

Thermodynamics of core hydrophobicity and packing in the hyperthermophile proteins Sac7d and Sso7d.

The influence of core hydrophobicity and packing on the structure and stability of the hyperthermophile proteins Sac7d and Sso7d have been studied by calorimetry, circular dichroism, and NMR. Valine 30 is positioned in Sac7d to allow a cavity-filling Val --> Ile substitution which occurs naturally in the homologous more thermostable Sso7d. The cavity-filling mutation in Sac7d has been characterized and compared to the reciprocal Ile --> Val mutation in Sso7d. A detailed analysis of the stability of the proteins was obtained by globally fitting the variation of DSC parameters and circular dichroism intensities as a function of temperature (0-100 degrees C), salt (0-0.3 M), and pH (0-8). A global analysis over such a range of conditions permitted an unusually precise measure of the thermodynamic parameters, as well as the separation of the thermodynamics of the intrinsic unfolding reaction from the linked effects of protonation and chloride binding associated with acid-induced folding. The results indicate differences in the energetics of unfolding Sac7d and Sso7d that would not be apparent from an analysis of DSC data alone using conventional methods. The sign and magnitude of the changes in DeltaG, DeltaH, TDeltaS, and DeltaC(P) of unfolding resulting from core Ile/Val substitutions in the two proteins were consistent with differences in hydrophobicity of Val and Ile and negligible changes in packing (van der Waals) interactions. The benefit of increased hydrophobicity of the core increased with temperature, with maximal effect around 116 degrees C. Increased hydrophobicity of the core achieved not only an increase in the free energy of unfolding, but also a lateral shift of the temperature of maximal stability to higher temperature.

Amino Acid Sequence↗
PubMedDate not supplied

Role of cross-linking agents in determining the biochemical and pharmacokinetic properties of Mgr6-clavin immunotoxins.

Several immunotoxins (ITs) were synthesized by the attachment of clavin, a recombinant toxic protein derived from Aspergillus clavatus, to the monoclonal antibody Mgr6 that recognizes an epitope of the gp185(HER-2) extracellular domain expressed on breast and ovarian carcinoma cells. Conjugation and purification parameters were analyzed in an effort to optimize the antitumor activity and stability of the ITs in vivo. To modulate the in vitro and in vivo properties of the immunotoxins, different coupling procedures were used and both disulfide and thioether linkages were obtained. Unhindered and hindered disulfide with a methyl group linkage ethyl S-acetyl 3-mercaptopropionthioimidate ester hydrochloride (AMPT) or ethyl S-acetyl 3-mercaptobutyrothioimidate ester hydrochloride (M-AMPT) were obtained by reaction with recombinant clavin, while the monoclonal antibody Mgr6 was derivatized with ethyl 3-[(4-carboxamidophenyl)dithio]propionthioimidate ester hydrochloride (CDPT). To achieve higher hindrance (a disulfide bond with a geminal dimethyl group), Mgr6 was derivatized with the N-hydroxysuccinimidyl 3-methyl-3-(acetylthio)butanoate (SAMBA) and clavin with CDPT. To evaluate the relevance of the disulfide bond in the potency and pharmacokinetic behavior of the ITs, a conjugate consisting of a stable thioether bond was also prepared by derivatizing Mgr6 with the N-hydroxysuccinimidyl ester of iodoacetic acid (SIA) and clavin with AMPT. The immunotoxins were purified and characterized using a single-step chromatographic procedure. Specificity and cytotoxicity were assayed on target and unrelated cell lines. The data indicate that the introduction of a hindered disulfide linkage into ITs has little or no effect on antitumor activity and suggest that disulfide cleavage is essential for activity; indeed, the intracellularly unbreakable thioether linkage produced an inactive IT. Analysis of IT stability in vitro showed that the release of mAb by incubation with glutathione is proportional to the presence of methyl groups and increases exponentially with the increase in steric hindrance. Analysis of the pharmacokinetic behavior of ITs in Balb/c mice given intravenous bolus injections indicated that ITs with higher in vitro stability were eliminated more slowly; i.e., the disulfide bearing a methyl group doubled the beta-phase half-life (from 3.5 to 7.1 h) compared with that of the unhindered, while a geminal dimethyl protection increased the elimination phase to 24 h. The thioether linkage showed its intrinsic stability with a beta-phase half-life of 46 h. The thioether linkage also increased the distribution phase from 17 to 32 min. The in vitro characteristics and in vivo stability of Mgr6-clavin conjugates composed of a methyl and dimethyl steric hindered disulfide suggest clinical usefulness.

Animals↗
PubMed2026

Photon-counting detector computed tomography (PCD-CT) in multiple myeloma: a systematic review and trial sequential meta-analysis on image quality and radiation dose.

OBJECTIVES: To systematically review and perform a meta-analysis comparing the effects of PCD-CT versus EID-CT on image quality (sharpness) and radiation dose (CTDIvol) in patients with bone lesions due to multiple myeloma&#xa0;(MM). METHODS: A comprehensive search of PubMed, Embase, Scopus, and Cochrane Central was conducted from inception to October 2025. Studies comparing PCD-CT and EID-CT in MM patients were included. Methodological quality was assessed using ROBINS-I, and the certainty of evidence was assessed using GRADE. RESULTS: A total of 41 studies were identified that matched our search criteria. After duplicate removal and screening, five studies (n = 170 patients) were included in the systematic review, with four contributing to the meta-analysis. PCD-CT showed a significant pooled mean difference in image sharpness (mean difference, + 0.99 points; 95% CI, 0.62-1.37; p < 0.001). PCD-CT also demonstrated a reduction in radiation dose (mean difference, -4.95 milligrays; 95% CI, -8.39 to -1.50; p = 0.005). Trial sequential analysis (TSA) confirmed stability of pooled estimates, with conclusive evidence for image sharpness improvement, and suggestive yet incomplete evidence for radiation dose reduction. CONCLUSION: Compared to EID-CT in MM, PCD-CT significantly improves subjective image sharpness as supported by trial sequential analysis. Conventional meta-analysis suggested a reduction in radiation dose with PCD-CT; however, trial sequential analysis indicated that the cumulative evidence remains inconclusive. Further large-scale studies are suggested to confirm the magnitude of the radiation dose reduction benefit.

Humans↗
PubMed2006

Quantitative analysis of an oligomeric hindered amine light stabilizer in polypropylene by matrix-assisted laser desorption/ionization mass spectrometry using a solid sampling technique.

A small amount of an oligomeric hindered amine light stabilizer (HALS) (Adekastab LA-68LD) in polypropylene (PP) materials was directly determined by solid sampling matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) using an internal standard method. First the matrix reagent (dithranol), 20 mg, and the empirically selected internal standard, angiotensin I (MW = 1296.5), 5 microg, were premixed in the solid state. The matrix mixture was then co-ground with the PP sample containing the HALS in liquid nitrogen using a freezer mill. The powdered sample mixture was spotted on the sample plate, suspended in ion-exchanged water, dried to adhere on the plate, and subjected to MALDI-MS. Three series of the HALS components accompanied by the oxidized species were clearly observed as their molecular ions (M*+)) along with that of the internal standard in the mass spectra. A fairly good linear relationship (R2 = 0.9991) with a relative standard deviation of ca. 11% was observed between the relative peak intensities of the HALS components and the HALS contents ranging from 0.1-2.5 wt%, which could be used as the calibration line to determine the HALS content in PP composites directly by MALDI-MS. The UV-exposed PP composite samples were evaluated by this method to interpret the photostabilizing action of HALS in the PP materials based on the observed change in the relative abundances of the original and oxidized HALS components as a function of UV-exposure time.

Journal Article↗
PubMed1999

Thermal stability of a flavoprotein assessed from associative analysis of polarized time-resolved fluorescence spectroscopy.

Upon gradually heating a particular mutant of the flavoprotein NADH peroxidase, it was found from the peculiar time-resolved fluorescence anisotropy pattern of the flavin prosthetic group (FAD) that, at elevated temperature, FAD is released from the tetrameric enzyme. Since in this case a mixture of free and enzyme-bound FAD contributes to the time-dependent fluorescence anisotropy, its analysis can only be accomplished by an associative fitting model, in which specific fluorescence lifetimes of both species are linked to specific correlation times. In this letter the general approach to the associative polarized fluorescence decay analysis is described. The procedure can be used for other flavoproteins to determine the temperature at which the onset of thermal denaturation will start, leading to release of the flavin prosthetic group.

Bacterial Proteins↗