New insights into precocious puberty and ADHD: a nationwide cohort study.

BACKGROUND: Attention deficit-hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders in children; however, studies delineating the association between ADHD and central precocious puberty are limited. This study aimed to understand whether children with ADHD are at a higher risk of central precocious puberty. METHODS: This population-based retrospective cohort study was conducted using the National Health Insurance Research Database of Taiwan to investigate the association between ADHD and the incidence of central precocious puberty between 2000-2015. We identified ADHD individuals treated with methylphenidate, atomoxetine or not. The control cohort consisted of individuals without ADHD. The outcome measure was central precocious puberty diagnosis. RESULTS: Among 290,148 children (mean age: 5.83 years), central precocious puberty incidence was 4.24 and 1.95 per 105 person-years in the ADHD and control groups, respectively. Children with ADHD treated with medication had a higher risk than those without ADHD. However, medication use did not affect the incidence of central precocious puberty among children with ADHD. CONCLUSION: This study showed an association between ADHD and a higher risk of central precocious puberty. Early referral of children with ADHD to a pediatric endocrinologist for evaluation may facilitate correct diagnoses and early interventions. IMPACT: ADHD is associated with a higher risk of central precocious puberty. This study provides relevant findings, as it is the first nationwide, population-based cohort study to investigate the association between ADHD and the risk of central precocious puberty with a 15-year follow-up. Early referral of children with ADHD to a pediatric endocrinologist for the evaluation of suspected precocious puberty could facilitate correct diagnosis. Early intervention treatment with gonadotropin-releasing hormone agonist might improve final height in children with central precocious puberty.

Baicalein ameliorates ulcerative colitis by improving intestinal epithelial barrier via AhR/IL-22 pathway in ILC3s.

Ulcerative colitis (UC) is a chronic inflammatory disease of the gastrointestinal tract, which is closely related to gut barrier dysfunction. Emerging evidence shows that interleukin-22 (IL-22) derived from group 3 innate lymphoid cells (ILC3s) confers benefits on intestinal barrier, and IL-22 expression is controlled by aryl hydrocarbon receptor (AhR). Previous studies show that baicalein protects the colon from inflammatory damage. In this study we elucidated the molecular mechanisms underlying the protective effect of baicalein on intestinal barrier function in colitis mice. Mice were administered baicalein (10, 20, 40 mg·kg-1·d-1, i.g.) for 10 days; the mice freely drank 3% dextran sulfate sodium (DSS) on D1-D7 to induce colitis. We showed that baicalein administration simultaneously ameliorated gut inflammation, decreased intestinal permeability, restored tight junctions of colons possibly via promoting AhR/IL-22 pathway. Co-administration of AhR antagonist CH223191 (10 mg/kg, i.p.) partially blocked the therapeutic effects of baicalein in colitis mice, whereas AhR agonist FICZ (1 µg, i.p.) ameliorated symptoms and gut barrier function in colitis mice. In a murine lymphocyte line MNK-3, baicalein (5-20 µM) dose-dependently increased the expression of AhR downstream target protein CYP1A1, and enhanced IL-22 production through facilitating AhR nuclear translocation, these effects were greatly diminished in shAhR-MNK3 cells, suggesting that baicalein induced IL-22 production in AhR-dependent manner. To further clarify that, we constructed an in vitro system consisting of MNK-3 and Caco-2 cells, in which MNK-3 cell supernatant treated with baicalein could decrease FITC-dextran permeability and promoted the expression of tight junction proteins ZO-1 and occluding in Caco-2 cells. In conclusion, this study demonstrates that baicalein ameliorates colitis by improving intestinal epithelial barrier via AhR/IL-22 pathway in ILC3s, thus providing a potential therapy for UC.

Baicalin prevents LPS-induced activation of TLR4/NF-κB p65 pathway and inflammation in mice via inhibiting the expression of CD14.

Previous studies have shown that baicalin, an active ingredient of the Chinese traditional medicine Huangqin, attenuates LPS-induced inflammation by inhibiting the activation of TLR4/NF-κBp65 pathway, but how it affects this pathway is unknown. It has been shown that CD14 binds directly to LPS and plays an important role in sensitizing the cells to minute quantities of LPS via chaperoning LPS molecules to the TLR4/MD-2 signaling complex. In the present study we investigated the role of CD14 in the anti-inflammatory effects of baicalin in vitro and in vivo. Exposure to LPS (1 µg/mL) induced inflammatory responses in RAW264.7 cells, evidenced by marked increases in the expression of MHC II molecules and the secretion of NO and IL-6, and by activation of MyD88/NF-κB p65 signaling pathway, as well as the expression of CD14 and TLR4. These changes were dose-dependently attenuated by pretreatment baicalin (12.5-50 µM), but not by baicalin post-treatment. In RAW264.7 cells without LPS stimulation, baicalin dose-dependently inhibit the protein and mRNA expression of CD14, but not TLR4. In RAW264.7 cells with CD14 knockdown, baicalin pretreatment did not prevent inflammatory responses and activation of MyD88/NF-κB p65 pathway induced by high concentrations (1000 µg/mL) of LPS. Furthermore, baicalin pretreatment also inhibited the expression of CD14 and activation of MyD88/NF-κB p65 pathway in LPS-induced hepatocyte-derived HepG2 cells and intestinal epithelial-derived HT-29 cells. In mice with intraperitoneal injection of LPS and in DSS-induced UC mice, oral administration of baicalin exerted protective effects by inhibition of CD14 expression and inflammation. Taken together, we demonstrate that baicalin pretreatment prevents LPS-induced inflammation in RAW264.7 cells in CD14-dependent manner. This study supports the therapeutic use of baicalin in preventing the progression of LPS-induced inflammatory diseases.

A Novel Multiprotein Bridging Factor 1-Like Protein Induces Cyst Wall Protein Gene Expression and Cyst Differentiation in Giardia lamblia.

The capacity to synthesize a protective cyst wall is critical for infectivity of Giardia lamblia. It is of interest to know the mechanism of coordinated synthesis of three cyst wall proteins (CWPs) during encystation, a differentiation process. Multiprotein bridging factor 1 (MBF1) gene family is a group of transcription coactivators that bridge various transcription factors. They are involved in cell growth and differentiation in yeast and animals, or in stress response in fungi and plants. We asked whether Giardia has MBF1-like genes and whether their products influence gene expression. BLAST searches of the Giardia genome database identified one gene encoding a putative MBF1 protein with a helix-turn-helix domain. We found that it can specifically bind to the AT-rich initiator promoters of the encystation-induced cwp1-3 and myb2 genes. MBF1 localized to cell nuclei and cytoplasm with higher expression during encystation. In addition, overexpression of MBF1 induced cwp1-3 and myb2 gene expression and cyst generation. Mutation of the helixes in the helix-turn-helix domain reduced cwp1-3 and myb2 gene expression and cyst generation. Chromatin immunoprecipitation assays confirmed the binding of MBF1 to the promoters with its binding sites in vivo. We also found that MBF1 can interact with E2F1, Pax2, WRKY, and Myb2 transcription factors that coordinately up-regulate the cwp genes during encystation. Using a CRISPR/Cas9 system for targeted disruption of mbf1 gene, we found a downregulation of cwp1-3 and myb2 genes and decrease of cyst generation. Our results suggest that MBF1 is functionally conserved and positively regulates Giardia cyst differentiation.

Oroxindin inhibits macrophage NLRP3 inflammasome activation in DSS-induced ulcerative colitis in mice via suppressing TXNIP-dependent NF-κB pathway.

Oroxindin is a flavonoid isolated from the traditional Chinese medicine Huang-Qin, which has shown various pharmacological activities including anti-inflammatory, antitumor, antioxidant, etc. Thus far, the effect of oroxindin on colonic inflammation and the underlying mechanism remain unknown. In this study, we investigated the tissue distribution of oroxindin and its therapeutic effects on ulcerative colitis (UC) as well as the underlying mechanisms. UC model was established in mice by administrating dextran sulfate sodium (DSS) in drinking water for 7 d. We first showed that oroxindin was largely absorbed by the colon as an active ingredient after normal mice received Huang-Qin-Tang, a traditional Chinese medicine decoction. UC mice were then treated with oroxindin (12.5, 25, 50 mg ·kg-1 ·d-1, i.g.) for 10 d. We found that oroxindin treatment greatly suppressed massive macrophages infiltration and attenuated pathological changes in colonic tissue. Furthermore, oroxindin treatment significantly inhibited the generation of IL-1ß and IL-18 in the colon via inhibiting the nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome formation and activation. In cultured macrophages, LPS induced NLRP3 inflammasome formation and caspase-1 activation, which were suppressed by oroxindin (12.5-50 µM). In LPS-treated macrophages, oroxindin dose-dependently restored the expression of TXNIP protein, leading to suppressing TXNIP-dependent NF-κB activation. In conclusion, these results demonstrate that oroxindin could be absorbed by the colon and attenuate inflammatory responses via inhibiting NLRP3 inflammasome formation and activation, which is related to the inhibitory effect on TXNIP-dependent NF-κB-signaling pathway. Hence, oroxindin has the potential of becoming an effective drug for treating UC.

Diagnosis and Surgical Outcomes of Patients with Anomalous Left Coronary Artery from the Pulmonary Artery: A Single Taiwanese Medical Center Experience.

BACKGROUND: Anomalous left coronary artery from the pulmonary artery (ALCAPA), a very rare congenital cardiac anomaly, is associated with a high mortality rate among infants who are not diagnosed or treated in a timely manner. Surgical intervention with the reconstruction for a two-coronary-system circulation is the main treatment; however, there have been very few reported cases from Taiwan. In this study, we aim to describe the clinical manifestations, diagnostic methods, surgery types, and surgical outcomes in patients with ALCAPA from a single Taiwanese medical center. METHODS: We retrospectively reviewed patients diagnosed with ALCAPA who underwent surgery at our institution between January 2001 and October 2018. Clinical presentations, noninvasive and invasive study results, surgical methods, and postoperative follow-up results were assessed from medical records. Moreover, literature on this particular cardiovascular anomaly was reviewed. RESULTS: The study included 6 patients (5 children and 1 adult). The diagnosis was confirmed using cardiac catheterization and coronary angiography in four patients and only echocardiography in two patients. All patients underwent surgical correction and survived. Four patients showed improvements in left ventricular function and mitral regurgitation (MR). CONCLUSION: Early diagnosis and timely surgical intervention could avoid mortality regardless of the method of operation. ALCAPA can be definitively diagnosed using noninvasive echocardiography. Both left ventricular systolic function and mitral insufficiency could improve after the surgical intervention in pediatric patients. Repair or replacement of the mitral valve could be reserved for persistent MR complicated with congestive heart failure, particularly in patients who received the initial operation beyond infancy.

A novel E2F-like protein involved in transcriptional activation of cyst wall protein genes in Giardia lamblia.

Giardia lamblia differentiates into resistant walled cysts for survival outside the host and transmission. During encystation, synthesis of cyst wall proteins is coordinately induced. The E2F family of transcription factors in higher eukaryotes is involved in cell cycle progression and cell differentiation. We asked whether Giardia has E2F-like genes and whether they influence gene expression during Giardia encystation. Blast searches of the Giardia genome database identified one gene (e2f1) encoding a putative E2F protein with two putative DNA-binding domains. We found that the e2f1 gene expression levels increased significantly during encystation. Epitope-tagged E2F1 was found to localize to nuclei. Recombinant E2F1 specifically bound to the thymidine kinase and cwp1-3 gene promoters. E2F1 contains several key residues for DNA binding, and mutation analysis revealed that its binding sequence is similar to those of the known E2F family proteins. The E2F1-binding sequences were positive cis-acting elements of the thymidine kinase and cwp1 promoters. We also found that E2F1 transactivated the thymidine kinase and cwp1 promoters through its binding sequences in vivo. Interestingly, E2F1 overexpression resulted in a significant increase of the levels of CWP1 protein, cwp1-3 gene mRNA, and cyst formation. We also found E2F1 can interact with Myb2, a transcription factor that coordinate up-regulates the cwp1-3 genes during encystation. Our results suggest that E2F family has been conserved during evolution and that E2F1 is an important transcription factor in regulation of the Giardia cwp genes, which are key to Giardia differentiation into cysts.

Factors Influencing the Reputation of Assistive Technology Resources Center: An Example from Yunlin County, Taiwan.

By the end of 2020, a total of 34 multifunctional Assistive Technology Resources Centers (ATR centers) were set up in 22 counties and cities in Taiwan. This study examines the perceptions of the users and their caregivers of the government-established ATR centers in Taiwan and examines the impact on the reputation of the public institution. The research framework and hypotheses were developed by examining the factors of "service convenience", "center-related factors", "justice", and "perceived value" and using "perceived value" as a mediating variable. The data were collected through a questionnaire survey, and the structural equation model was used to test the model and verify the hypotheses. Research data was collected in various townships in Yunlin County A total of 320 questionnaires were collected. Of these respondents, 22% were aged 51-60. All the research hypotheses were positively and significantly verified. Of these, justice was the most important factor affecting the value of the ATR center's services compared to convenience and center-related factors. Of convenience, service value and justice, service value was the most important factor affecting the perceived reputation of the public institution. According to the findings of this study, it is beyond expectation that the convenience of ATR is not the main factor influencing the service value, but rather the perceived justice is the most important factor. Therefore, ATR should be prioritized from the perspective of the service recipient, especially the perceived justice of the service, in order to best enhance the value of the service and improve the reputation of the public institution.

Positive Association Between Fluoroquinolone Exposure and Tendon Disorders: A Nationwide Population-Based Cohort Study in Taiwan.

Introduction: Fluoroquinolone exposure is reportedly associated with a higher risk of tendon disorders, tendonitis, or tendon rupture. However, studies in East Asian populations have not confirmed these risks in patients with comorbidities or concomitant medication use. This cohort study was designed to investigate the associations among fluoroquinolone exposure, comorbidities, medication use, and tendon disorders in Taiwan. Materials and Methods: This population-based, nationwide, observational, cohort study used data from the National Health Insurance Research database in Taiwan, a nationwide claims database that covers more than 99% of the Taiwanese population. The study period was from January 2000 to December 2015, and the median follow-up time was 11.05 ± 10.91 years. Patients who were exposed to fluoroquinolones for more than three consecutive days were enrolled, and patients without fluoroquinolone exposure who were matched by age, sex, and index year were enrolled as controls. The associations of comorbidities and concomitant medication use with tendon disorder occurrence were analyzed using Cox regression models. Results: The incidence of tendon disorders were 6.61 and 3.34 per 105 person-years in patients with and without fluoroquinolone exposure, respectively (adjusted hazard ratio, 1.423; 95% confidence interval [1.02,1.87]; p = 0.021). Sensitivity analyses yielded similar results. Patients under 18 and over 60 years with fluoroquinolone exposure; those with chronic kidney disease, diabetes, rheumatologic disease, cardiac disease, lipid disorder, or obesity; and those who concomitantly used statins, aromatase inhibitors, or glucocorticoids, had a significantly higher risk of tendon disorders. Conclusion: The long-term risk of tendon disorders was higher in patients with fluoroquinolone exposure than in those without fluoroquinolone exposure. Clinicians should assess the benefits and risks of fluoroquinolone use in patients at high risk of tendon disorders who require fluoroquinolone administration.

Implantation of monocusp valve prolongs the duration of chest tube drainage in children with tetralogy of fallot after corrective surgery.

BACKGROUND: Right ventricular outflow tract obstruction relief is one of the major procedures during the total correction of tetralogy of Fallot (TOF). Pulmonary insufficiency (PI) is usually inevitable after a transannular incision with a patch repair is performed. Therefore, some surgeons advocate to place a monocusp valve within the transannular patch (TAP) in order to decrease the severity of the PI. However, the monocusp valve seemed not be very effective in some patients who underwent the complete TOF repair. METHODS: Patients who had the classic form of TOF between January 2009 and January 2017 and underwent the corrective surgery with a TAP by the same cardiovascular surgeon were identified for further analysis. Clinical information including demographics at operation, perioperative data, and postoperative outcome were collected retrospectively and compared between the group with and without a monocusp valve. RESULTS: A total of 24 TOF cases were included in the final analysis, and 16 (66.7%) patients received a monocusp valve placement. The patients' characteristics before and during the surgery were similar between the two groups. The median duration of chest tube drainage after the total correction in the monocusp group was longer than those without the valve (p = 0.04). There was no difference in the immediate postoperative data, including the inflammation/infection status, the duration of mechanical ventilation, and the length of ICU and hospital stay. CONCLUSION: Implantation of a monocusp valve during the total TOF correction using a TAP did not bring benefit to improve the immediate postoperative outcomes, especially the duration of the pleural drainage. Further study with a prospective design and a larger number of cases is needed.

Association Between Tetralogy of Fallot and Psychiatric Disorders: A Nationwide Cohort Study.

OBJECTIVE: The tetralogy of Fallot (TOF) has been reported to be associated with some neurodevelopmental impairment and psychiatric disorders. Nevertheless, a nationwide study to clarify the risk between TOF and comorbid psychiatric disorders is lacking. Using a nationwide database in Taiwan, this study aimed to explore the role of TOF in various psychiatric disorders and analyze whether there are patient-related risk factors. METHODS: A total of 16,824 enrolled patients, including 4,206 study subjects who were diagnosed with TOF and 12,618 controls with TOF matched (1:3) for sex, age, hospital visits, and index year, were randomly selected from the Taiwanese National Health Insurance Research Database (NHIRD) between 2000 and 2015. Patients' diagnoses in the NHIRD were encoded using International Classification of Diseases, 9th Revision, Clinical Modification codes. RESULTS: Of patients with TOF, 256 (6.09%) developed psychiatric disorders compared to 394 (3.12%) in the control group. After adjusting for covariates, the adjusted hazard ratio of psychiatric disorders for patients with TOF was 3.192 (95% CI, 2.683-3.798; P < .001). After exclusion of psychiatric diagnoses within the first 5 years, TOF was associated with an increased risk of anxiety (P < .001), depression (P < .001), bipolar disorder (P < .001), and sleep disorders (P = .005). CONCLUSIONS: This study revealed that TOF patients have a nearly 3-fold higher risk of psychiatric disorders, including anxiety, depressive, bipolar, and sleep disorders, than the general population. Therefore, continued mental health screening and surveillance are warranted in TOF patients.

Social Image Impacting Attitudes of Middle-Aged and Elderly People toward the Usage of Walking Aids: An Empirical Investigation in Taiwan.

The elderly need the assistance of walking aids due to deterioration of their physical functions. However, they are often less willing to use these aids because of their worries about how others may think of them. Not using professional walking aids often makes elderly people fall easily when walking. This study explores the behavioral intention factors of middle-aged people (45-64 years old) and elderly people (65 years and older) that affect the use of walking aids. Based on the Theory of Reasoned Action (TRA), subjective norms, attitude toward usage, behavior intention, safety, and usefulness were combined with social image to establish the research framework. This study used questionnaire surveys both in paper form assisted by volunteers and in online electronic form. A total of 457 questionnaires were collected. Data analysis was carried out in three stages: descriptive analysis, measurement model verification, and structural equation model analysis. The results showed that social image had a significant impact on the attitude toward using walking aids. Factors such as attitude toward usage, subjective norms, and safety of walking aids also had a significant positive impact on behavioral intention. Finally, through the research results, some suggestions are proposed for stakeholders to improve the elderly's concerns about the social image of using walking aids.

Ethyl 7-chloro-methyl-5-(2-chloro-phen-yl)-7-hydr-oxy-2-methyl-sulfanyl-4,5,6,7-tetra-hydro-1,2,4-triazolo[1,5-a]pyrimidine-6-carboxyl-ate.

In the title compound, C(16)H(18)Cl(2)N(4)O(3)S, the five-membered ring is almost planar [maximum deviation = 0.011 (3) Å] and the six-membered ring adopts an envelope conformation. In the crystal structure, N-H⋯N, O-H⋯N and C-H⋯O inter-actions link mol-ecules into a three-dimensional network.

Deriving protein dynamical properties from weighted protein contact number.

It has recently been shown that in proteins the atomic mean-square displacement (or B-factor) can be related to the number of the neighboring atoms (or protein contact number), and that this relationship allows one to compute the B-factor profiles directly from protein contact number. This method, referred to as the protein contact model, is appealing, since it requires neither trajectory integration nor matrix diagonalization. As a result, the protein contact model can be applied to very large proteins and can be implemented as a high-throughput computational tool to compute atomic fluctuations in proteins. Here, we show that this relationship can be further refined to that between the atomic mean-square displacement and the weighted protein contact-number, the weight being the square of the reciprocal distance between the contacting pair. In addition, we show that this relationship can be utilized to compute the cross-correlation of atomic motion (the B-factor is essentially the auto-correlation of atomic motion). For a nonhomologous dataset comprising 972 high-resolution X-ray protein structures (resolution <2.0 A and sequence identity <25%), the mean correlation coefficient between the X-ray and computed B-factors based on the weighted protein contact-number model is 0.61, which is better than those of the original contact-number model (0.51) and other methods. We also show that the computed correlation maps based on the weighted contact-number model are globally similar to those computed through normal model analysis for some selected cases. Our results underscore the relationship between protein dynamics and protein packing. We believe that our method will be useful in the study of the protein structure-dynamics relationship.

On the relationship between the protein structure and protein dynamics.

Recently, we have developed a method (Shih et al., Proteins: Structure, Function, and Bioinformatics 2007;68: 34-38) to compute correlation of fluctuations of proteins. This method, referred to as the protein fixed-point (PFP) model, is based on the positional vectors of atoms issuing from the fixed point, which is the point of the least fluctuations in proteins. One corollary from this model is that atoms lying on the same shell centered at the fixed point will have the same thermal fluctuations. In practice, this model provides a convenient way to compute the average dynamical properties of proteins directly from the geometrical shapes of proteins without the need of any mechanical models, and hence no trajectory integration or sophisticated matrix operations are needed. As a result, it is more efficient than molecular dynamics simulation or normal mode analysis. Though in the previous study the PFP model has been successfully applied to a number of proteins of various folds, it is not clear to what extent this model will be applied. In this article, we have carried out the comprehensive analysis of the PFP model for a dataset comprising 972 high-resolution X-ray structures with pairwise sequence identity or=0.5. Our result shows that the fixed-point model is indeed quite general and will be a useful tool for high throughput analysis of dynamical properties of proteins.

[Separation and purification of flavonoids from Smilax glabra by macroporous adsorption resin].

OBJECTIVE: To investigate the process of separating and purifying flavonoids from Smilax glabra. METHOD: With the yield of flavonoids as index, the optimum process of separating and purifying flavonoids from S. glabra Roxb was screened by static and dynamic adsorption tests. RESULT: The static saturated adsorption capacity of D101 macroporous resin to flavonoids of S. glabra was 45.6 mg x g(-1) (dry resin). The optimum conditions of dynamic adsorption and elution were as that the pH, the concentration, the adsorption velocity of the extracting solution, and the adsorption capacity were 6.00 +/- 0.20, 4.2 mg x mL(-1), 2 mL x min(-1) and 15 mL, respectively. The adsorbed resin column was washed by 100 mL 60% ethanol with pH value of 8.00 +/- 0.20 at the eluting velocity of 3 mL x min(-1) after washed by 100 mL distilled water. CONCLUSION: The flavonoids of S. glabra was able to be easily separated and purified by D101 macroporous resin under the optimum conditions above, and the recovery rate was higher than 90%. The content of obtained flavonoids reached 62.6%, which was 2 times of the content before purification.

A simple way to compute protein dynamics without a mechanical model.

We found that in proteins the average atomic fluctuation is linearly related to the square of the atomic distance from the center of mass of the protein. Using this simple relation, we can accurately compute the temperature factors of proteins of a wide range of sizes and folds, and the correlation of the fluctuations in proteins. This simple relation provides a direct link between protein dynamics and the static protein's geometrical shape and offers a simple way to compute protein dynamics without either long time trajectory integration or any matrix operations.

[Extracting flavonoids from Smilax glabra by microwave-assisted method].

OBJECTIVE: To optimize the process of extracting flavonoids from Smilax glabra. METHODS: Flavonoids were extracted from Smilax glabra by microwave-assisted method, and the extracting time, microwave power, ethanol concentration, solid-solvent ratio and extracting temperature were optimized through single factor experiment and orthogonal test. RESULTS: The optimun process parameters of extracting flavonoids were as follows: the extracting time, microwave power, ethanol concentration, solid-liquid ratio and extracting temperature were 5 minutes, 600 W, 60%, 1:30 and 80 degrees C, respectively. CONCLUSION: The proposed method has been applied stably and reliably to the extraction of flavonoids from Smilax glabra which has the advantages of high recovery and short extraction time. The recovery, the yield and the content of falvonoids are 93.2%, 2.66% and 32.6%, respectively.

Computation of conformational entropy from protein sequences using the machine-learning method--application to the study of the relationship between structural conservation and local structural stability.

A complete protein sequence can usually determine a unique conformation; however, the situation is different for shorter subsequences--some of them are able to adopt unique conformations, independent of context; while others assume diverse conformations in different contexts. The conformations of subsequences are determined by the interplay between local and nonlocal interactions. A quantitative measure of such structural conservation or variability will be useful in the understanding of the sequence-structure relationship. In this report, we developed an approach using the support vector machine method to compute the conformational variability directly from sequences, which is referred to as the sequence structural entropy. As a practical application, we studied the relationship between sequence structural entropy and the hydrogen exchange for a set of well-studied proteins. We found that the slowest exchange cores usually comprise amino acids of the lowest sequence structural entropy. Our results indicate that structural conservation is closely related to the local structural stability. This relationship may have interesting implications in the protein folding processes, and may be useful in the study of the sequence-structure relationship.