Statistical Analysis of the Role of Cavity Flexibility in Thermostability of Proteins.

Conventional statistical investigations have primarily focused on the comparison of the simple one-dimensional characteristics of protein cavities, such as number, surface area, and volume. These studies have failed to discern the crucial distinctions in cavity properties between thermophilic and mesophilic proteins that contribute to protein thermostability. In this study, the significance of cavity properties, i.e., flexibility and location, in protein thermostability was investigated by comparing structural differences between homologous thermophilic and mesophilic proteins. Three dimensions of protein structure were categorized into three regions (core, boundary, and surface) and a comparative analysis of cavity properties using this structural index was conducted. The statistical analysis revealed that cavity flexibility is closely related to protein thermostability. The core cavities of thermophilic proteins were less flexible than those of mesophilic proteins (averaged B' factor values, -0.6484 and -0.5111), which might be less deleterious to protein thermostability. Thermophilic proteins exhibited fewer cavities in the boundary and surface regions. Notably, cavities in mesophilic proteins, across all regions, exhibited greater flexibility than those in thermophilic proteins (>95% probability). The increased flexibility of cavities in the boundary and surface regions of mesophilic proteins, as opposed to thermophilic proteins, may compromise stability. Recent protein engineering investigations involving mesophilic xylanase and protease showed results consistent with the findings of this study, suggesting that the manipulation of flexible cavities in the surface region can enhance thermostability. Consequently, our findings suggest that a rational or computational approach to the design of flexible cavities in surface or boundary regions could serve as an effective strategy to enhance the thermostability of mesophilic proteins.

Gd-DTPA Enhanced MRI of the Brain Infarction: Correlation between Onset of Infarction and Enhancing Patterns

PURPOSE: To evaluate the correlation between onset of brain infarction and Gd-DTPA enhancing patterns on MRI. MATERIALS AND METHODS: We reviewed MRI of 58 lesions in 45 patients with clinically documented brain infarction retrospectively. Axial, coronal and sagittal T1WI (TR/TE 450-520/20), T2WI (TR/TE 2190/90) and Gd-DTPA enhanced T1WI were performed with a 0.5T superconductive MR system. We analyzed Gd-enhancing patterns lhat were divided into intravascular, meningeal, and parenchymal enhancement. Parenchymal pattern was subdivided into mottled, partial ring like and dense enhancement. RESULTS: lntravascular enhancement was seen at 1-10 days in 30(53%) of 58 infarctions. Meningeal enhancement (13%) was noted at 1--6 days. Parenchymal enhancement (50%) was seen at 2--28 days and subdividing patterns are as follows:The mottled enhancement pattern was seen earlier at 2-8 days and partial ring like or dense enhancement patterns at 5-28 days. CONCLUSION: After reviewing Gd-enhanced MRI of infarction, the intravascular and meningeal enhancement patterns were earlier than parenchymal enhancement. Among parenchymal patterns, the mottled pattern was seen earlier than partial ring like or dense patterns. In conclusion, Gd-enhancing patterns of brain infarction are useful in estimating the age of infarction including acute infarction.

MR Findings of Laryneal Cancer: Pathologic Correlation

PURPOSE: MRI is known to display the anatomy of the larynx in excellent detail with its remarkable soft tissue delineation and multiplanar imaging capability. We evaluate the accuracy of MRI in diagnosis and staging of laryngeal cancer MATERIALS AND METHODS: Sixteen cases with pathologically proved squamous cell carcinoma of the larynx were reviewed, retrospectively. The examination was performed with a 0.5 T superconductive MR system and C1 surface coil. Axial, sagittal and coronal plane with T1WI(TR/TE 450/20) and T2WI(TR/TE 18OO/80) were done. RESULTS: Eleven cases with glottic cancer(5 Tla, 3 Tlb, 1 T3 and 2 T4) and 5 cases with supraglottic cancer (1 T1, 1 T3 and 1 T4) were included. Cancer tissue showed intermediate signal intensity on TIWI and high signal intensity on T2Wl. Among 16 cases, 13 cases were correctly staged and 3 cases were overstaged due to edema caused by previous biopsy, partial volume averaging effect of abutted lesion, or surrounding inflammation. CONCLUSION: MRI is an useful modality for diagnosis of laryngeal cancer, especially in evaluation of paraglottic extention on coronal image and cartilage invasion.