Biomedical subjects

S J Lin

Publications and source records attributed to S J Lin.

At least 55 records · Page 3Linked to original sources

PubMed2000

Identification of the spinocerebellar ataxia type 7 mutation in Taiwan: application of PCR-based Southern blot.

Spinocerebellar ataxia (SCA) type 7 is an autosomal dominant disorder characterized by neural loss, mainly in the cerebellum and regions of the brainstem and particularly the inferior olivary complex. This neurodegeneration disease is associated with expansion of unstable CAG repeats within the 5'-translated region of the SCA7 gene, located on chromosome 3p. We conducted a local survey of the normal population and candidate patients for the analysis of the CAG repeats in the SCA7 gene. The distributions of the CAG repeat units of SCA7 gene in the normal population in Taiwan were established in this study by using the radioactive genomic polymerase chain reaction (PCR). The normal range of CAG repeats is from 6 to 17 repeats, with the more common being around 8-13 repeats. The range is narrower than that reported for other ethnic groups (7-35 CAGs). Meanwhile, by the use of a combination of PCR and Southern blot analysis, one SCA7 family was identified and is reported here. A marked instability of the CAG repeat number during transmission from father to son (41 vs. 100) was observed in the SCA7 family. Clinical anticipation is significant in this family including an infantile case, who was found to have nystagmus from the age of 1 month. To date, the SCA7 mutation has been detected in one of 73 families with autosomal dominant cerebellar ataxia phenotypes, which is about 1.4% of the ataxia families referred to us, compared to 1.4% SCA1, 9.6% SCA2, and 27.3% SCA3/Machado-Joseph disease in our collection. In addition, we demonstrate that the PCR-based Southern blot analysis, with the advantages of sensitivity of PCR and specificity of Southern blot, is a reliable diagnostic method for SCA7 mutation screening. The molecular analysis technique makes possible the quick and accurate diagnosis of SCA7 patients and in the future will hopefully be applied to prenatal screening for SCA7 families.

Adolescent↗

PubMed2000

Different articular outcomes of Still's disease in Chinese children and adults.

The clinical manifestations, treatment and course, and articular outcomes of 24 children with juvenile-onset Still's disease (JOSD) and 21 adults with adult-onset Still's disease (AOSD) were compared retrospectively. There was no significant difference in the initial clinical and laboratory manifestations except that more adults presented with a sore throat (81% vs. 46%, p = 0.03). Although serum ferritin was almost always elevated in both diseases, adults had significantly higher serum ferritin concentrations compared with those of children. Steroid treatment was required in 71% of children and 52% of adults, while disease-modifying antirheumatic drugs were used in 42% of children and 24% of adults during the course. Chronic arthritis (>6 months) occurred in comparable proportions of patients with JOSD and AOSD (46% vs 38%, p = 0.82), irrespective of the disease pattern (monocyclic or polycyclic). However, severe deforming arthritis with marked functional limitation occurred only in JOSD, particularly with polyarthritis at disease onset (more than five affected joints). In contrast, AOSD patients with chronic arthritis had a favourable functional outcome at the end of the follow-up. Our study suggested different articular outcomes of Still's disease in Chinese children and adults.

Adolescent↗

PubMed2000

Differential coronary hemodynamics and left ventricular contractility in patients with syndrome X.

The relationship between coronary hemodynamics and left ventricular contractility was studied in 20 patients with syndrome X. Among them, 10 patients with a resting left ventricular ejection fraction (LVEF, by radionuclide method) equal to or greater than the mean value of the whole group (58%) were defined as having relative increased left ventricular contractility (group H), and another 10 patients with relatively normal contractility (50%</=LVEF<58%) were in group N. Eight subjects with normal contractility, exercise test and coronary angiograms served as the control (group C). Baseline great cardiac venous flow (GCVF) was higher in group N than in group H (P<0.05) and C (P<0.05), but similar between group H and C. After dipyridamole infusion (0.56 mg/kg, i.v., for 4 min), maximum GCVF was less in group H than in group N (P<0.001) and C (P<0.001), but similar between group N and C. As compared to group C (3.09+/-0.35), coronary flow reserve was reduced in both group H (2.34+/-0.55, P=0. 004) and N (2.40+/-0.36, P=0.001). In all syndrome X patients, resting LVEF was negatively correlated to baseline GCVF (P=0.026) and tended to be positively correlated to baseline coronary vascular resistance (P=0.057). Thus, coronary hemodynamics was altered with left ventricular contractility in syndrome X patients. In these patients, coronary flow reserve was similarly reduced with different underlying mechanisms. The limited increase of GCVF after dipyridamole infusion suggests impaired coronary microvascular dilation capacity in patients with relatively increased left ventricular contractility and the increase of baseline GCVF in those with normal contractility is more likely due to an altered basal myocardial metabolism.

Adult↗

PubMed2000

Bacterial morphotypes and early cellular responses in clinically infected and non-infected sites after combination therapy of guided tissue regeneration and allograft.

OBJECTIVES: To compare the bacterial morphotypes and early cellular responses in periodontally treated sites with and without pus formation after a combination of guided tissue regeneration (GTR) and allograft therapy. METHODS: 45 subjects with 80 sites having periodontal lesions with moderate to deep pockets and angular bone defects participated. 28 treated sites in 25 patients were included in the studies. 14 sites suffered from symptoms and signs of infection with pus formation during the healing period were assigned to the pus (P) group. Another 14 sites had asymptomatic healing and were assigned to the non-pus (NP) group. The GTR membranes were retrieved 4-6 weeks after surgery and processed for SEM examination. The bacterial morphotypes on the membranes were observed and photographed. Bacterial adhesion score (BAS, 0-5) and the presence of leukocytes and fibroblasts were estimated from photographs. RESULTS: The results showed that large numbers of bacteria (high BAS) were present on both sides of the coronal 2/3 of the membrane in both groups, irrespective of clinical conditions. At the apical 1/3 of the membrane, moderate numbers of bacteria were still found on the outer side in the P group. The BAS of rod-shaped bacteria were significantly higher in the P group than that of the NP group on the outer coronal 2/3 of the membrane. The frequency of the presence of fibroblasts (18.5%) at the apical 1/3 of the inner (tooth facing) side of the P group was much lower than that of the same location (28.6-29.6%) in the NP group. The presence of leukocytes and fewer numbers of fibroblasts on the GTR membrane were associated with greater BAS for rod- and filament-shaped bacteria. CONCLUSIONS: GTR membranes are commonly colonized by oral bacteria during retention, even on uncomplicated and tissue covered portions. The overt infection clinically (pus group) of the membrane-allograft treated sites is associated with a significantly elevated BAS of rod-shaped bacteria, and may be closely related to the occurrence of its adverse early healing responses (inflammation, pus formation, fewer fibroblasts and greater accumulation of leukocytes).

Adult↗

PubMed2000

Ras signaling is involved in the expression of Fas-L in glioma.

Fas-L expresses on a variety of tumors and is suspected to modify the dialog between tumor and the immune system. However, the cellular abnormality in tumor cells leading to an aberrant expression of Fas-L is unclear. In this study, we demonstrate the involvement of Ras signaling in the Fas-L expression in several ways. First, the activated Ha-rasval12 gene enhanced the Fas-L expression of primary human glial cells. Second, blocking the Ras signal pathway in glioma cells by lovastatin or the Ha-rasAsn17 dominant-negative mutant gene resulted in reduced Fas-L expression. Transfection of the Ha-rasAsn17 into glioma cells also inhibited the activation of NFKB, which is a downstream component of Ras signaling. Accordingly, the membrane-permeable NFKB competitor suppressed the Fas-L expression. Furthermore, the Fas-L expression coincided with the Ras activity in the murine 212 cells, in which the Ras activity could be induced by isopropyl 3-D-thiogalactoside. In summary, these results suggest that the enhanced Ras signaling with consequential NFKB activation, which is a frequent defect found in tumors, could mediate the Fas-L expression of tumors.

Antineoplastic Agents↗

PubMed2000

ICAM-1 (CD54) expression on T lymphocytes and natural killer cells from umbilical cord blood: regulation with interleukin-12 and interleukin-15.

We investigated the effect of two immunoregulatory cytokines, interleukin (IL)-12 and IL-15, alone or in combination, on intercellular adhesion molecule 1 (ICAM-1, CD54) expression on mononuclear cells (MNC) obtained from umbilical cord blood (CB) and adult peripheral blood (APB). We established that (1) ICAM-1 expression was deficient on freshly isolated CB T and natural killer (NK) cells compared with that on adult cells; (2) ICAM-1 expression on T cells (CD3+/CD54+), but not on NK cells (CD16+/CD54+), was spontaneously upregulated after 7 days' culture in RPMI with 10% fetal calf serum (FCS) in the absence of cytokines, for CB and APB MNC alike; (3) removal of 10% FCS from the medium did not affect the spontaneous CD3+/CD54+ upregulation on APB MNC; (3) CB NK cells responded more readily to IL-12 and IL-15 than did APB NK cells in terms of ICAM-1 expression, while ICAM-1 expression on APB T cells, but not on CB T cells, could be enhanced with IL-12 plus IL-15; (4) the combination of IL-12 and IL-15 downregulated ICAM-1 expression on both CB and APB NK cells. Thus, we demonstrated the different patterns of ICAM-1 regulation by CB MNC and APB MNC in response to IL-12 and/or IL-15 and the differential effect of cytokines on the regulation of adhesion molecules on neonatal NK and T cells.

Adult↗

PubMed2000

Implication of screening for FMR1 and FMR2 gene mutation in individuals with nonspecific mental retardation in Taiwan.

Fragile X syndrome (FXS) is the most common form of familial mental retardation (MR), attributable to (CGG)n expansion in the FMR1 gene. FRAXE is less frequent, associated with a similar mutation of the FMR2 gene. This study attempted to ascertain the prevalence of both disorders in Taiwan, as well as to develop a method to effectively find carriers. A total of 321 patients with nonspecific MR were screened for the FMR1 and FMR2 mutation. Four of 206 boys and men (1.9%) and 1 in 115 girls and women (0.9%) were identified as having FXS. All four FXS boys or men could be identified by Southern blot analysis, as well as by a simple nonradioactive polymerase chain reaction analysis. None of the 206 boys or men had FMR2 full mutation. This confirmed the low incidence of FRAXE in Chinese. FXS appears to be more prevalent among patients with mild MR, because 4 of the 5 patients with FXS were from the 115 with mild MR (3.48%) and only 1 was from the other 206 with severe MR (0.49%). All five FXS cases were maternally inherited. Other family members were resistant to further searching for carriers. It is worth noting that none of these mothers had a discernible premarital family history of MR. Thus the negative family history could not preclude the possibility that a woman was a carrier. To identify female carriers of childbearing age, beyond the scope of family history, is thus worthy of further exploration. Screening men for carriers using this inexpensive method is probably feasible, even though normal transmitting men have no immediate risk of producing a child with the disease. Female carriers can then be effectively identified from these normal transmitting men and can take all preventive measures.

Adolescent↗

PubMed2000

The effect of interleukin-12 and interleukin-15 on CD69 expression of T-lymphocytes and natural killer cells from umbilical cord blood.

We investigated the effect of two immunoregulatory cytokines interleukin-12 (IL-12) and IL-15, alone or in combination, on CD69 expression of mononuclear cells (MNCs) obtained from umbilical cord blood (CB) and adult peripheral blood (APB). We established that (1) CD3/69, but not CD16/69, expression on CB MNCs could be increased with IL-12, IL-15 or both in 18-hour cultures, but to a lesser degree compared to that on corresponding APB MNCs, (2) CD3/69 expression on CB MNCs was significantly increased after 1 week's culture with IL-12, especially with IL-15, exceeding that on APB MNCs similarly activated and (3) CD16/69 expression on CB MNCs, but not APB MNCs, was greatly increased after 1 week's culture with IL-15. The combination of IL-12 + IL-15 resulted in greater CB CD3/69 expression than individual cytokines, while producing less of an effect on CD16/CD69 expression as compared to IL-15 alone. The results of our study indicate that neonatal T and NK cells readily respond to cytokine stimulation by upregulating CD69 expression, with a greater effect achieved using IL-15 compared to IL-12.

Adult↗

PubMed2000

Sonographic evaluation of cellulitis in children.

Within a 3 year period from July 1996 to July 1999, a total of 105 children with clinical diagnosis of cellulitis were evaluated by ultrasonography. Eighty-six children (age range, 17 days to 15 years) fulfilling the sonographic criteria for diagnosis of cellulitis were enrolled into the study. The sonographic features were used to correlate with clinical symptoms and their duration, the peripheral leukocyte count, and the serum C-reactive protein level. Pus aspiration for immediate microscopic and later bacteriologic studies was carried out under sonographic guidance. Ultrasonographic features of cellulitis included subcutaneous tissue thickening without distortion and pus (25 cases, 29%), distortion of subcutaneous tissue without pus accumulation (26 cases, 30%), distortion of subcutaneous tissue with pus accumulation (19 cases, 23%), and distortion of tissue with abscess formation (16 cases, 18%). The presence of sonographic features of tissue distortion with or without pus accumulation, including abscess formation in children with cellulitis, correlated with a longer duration of symptoms (greater than 4 days), the presence of high-grade fever, higher peripheral leukocyte count, and higher serum C-reactive protein levels. Those patients who underwent sonographically guided aspiration or surgical intervention showed a shorter hospital stay and fever duration than those without such aspiration. Our results indicated that ultrasonography is of great value in managing cellulitis by providing information regarding the progression of inflammation. Sonographically guided aspiration of pus may be a treatment of choice, as it may decrease the need for operation.

Adolescent↗

PubMed2000

Sonographic evaluation of the pancreatic duct in normal children and children with pancreatitis.

We investigated the diameter of pancreatic duct using ultrasonography in 51 children with pancreatitis and age-matched healthy control children over a 5 year period. The diameters of pancreatic duct and pancreatic body were measured simultaneously by sonography. The mean ages of children with acute pancreatitis and chronic pancreatitis were 9.7 +/- 3.9 and 10.3 +/- 3.1 years, respectively (range, 1 to 8 years). The mean age of normal children was 9.6 +/- 5.3 years. A significant difference was found in diameter of the pancreatic duct between children with acute and chronic pancreatitis versus that of age-matched control. In addition, a significant difference in diameter of the pancreatic body was found between children with acute pancreatitis and age-matched controls, but there was no marked difference in diameter of the pancreatic body between normal persons and those with chronic pancreatitis. The mean diameters of the pancreatic duct in acute pancreatitis and chronic pancreatitis were 2.34 +/- 0.47 mm and 2.84 +/- 0.67 mm, respectively, which was greater than that of normal children (1.65 +/- 0.45 mm). Pancreatic ducts with diameters greater than 1.5 mm in children between 1 and 6 years, greater than 1.9 mm at ages 7 to 12 years, or greater than 2.2 mm at ages 13 to 18 years were significantly associated with the presence of acute pancreatitis. Thirty-two patients, including 25 with acute pancreatitis and 7 with chronic pancreatitis, underwent follow-up measurement of pancreatic duct and serum lipase examination on at least three occasions. A good correlation between the diameter of pancreatic duct and serum lipase level was found. Thus, ultrasonography of the pancreatic duct is valuable in diagnosis and monitoring of pancreatitis in children.

Adolescent↗

PubMed2000

Sonographic features related to volvulus in neonatal intestinal malrotation.

This 3 year prospective study evaluated the sensitivity and specificity of abdominal ultrasonography and color Doppler ultrasonography in 31 neonates with suspected malrotation or malrotation with volvulus. Water instillation was used to detect duodenal dilatation, edema, and malrotated bowels. Twenty patients with ultrasonographic characteristics of inversion of the superior mesenteric artery and superior mesenteric vein were later surgically proved to have malrotation. Nine of these 20 patients also had volvulus. Sonographic features suggestive of volvulus included duodenal dilation with tapering configuration (8 of 9 cases, 89%), fixed midline bowel (8 of 9 cases, 89%), whirlpool sign (8 of 9 cases, 89%), and dilation of the distal superior mesenteric vein (5 of 5 cases, 100%). The sensitivity and specificity of duodenal dilation with tapering configuration for detecting volvulus were 89% and 92%, respectively; of fixed midline bowel, 89% and 92%; of whirlpool sign, 89% and 92%; and of dilation of distal superior mesenteric vein, 56% and 73%. The results of this study indicate that ultrasonographic features of inversion of the superior mesenteric artery and superior mesenteric vein could aid in the diagnosis of malrotation, and certain sonographic features can also be used to evaluate volvulus, a condition requiring emergent operation.

Blood Flow Velocity↗

PubMed2000

Diffuse multiple coronary arteries to left ventricular fistulas.

Coronary artery to left ventricular fistula is an unusual anatomic anomaly consisting of a communication between one of the coronary arteries and the left ventricle. Only sporadic cases have been published in the literature. Diffuse multiple fistulas involving both left and right coronary arteries are even rarer. This report describes a 60-year-old woman with diffuse multiple fistulas communicating between both coronary arteries and the left ventricle. The patient manifested clinically with exertional angina and myocardial ischemia, as evidenced by a positive stress exercise test, which represents the coronary "steal" phenomenon.

Coronary Vessel Anomalies↗

PubMed2000

Effect of interleukin-15 and Flt3-ligand on natural killer cell expansion and activation: umbilical cord vs. adult peripheral blood mononuclear cells.

Expansion and activation of cord blood (CB) natural killer (NK) cells by cytokines might greatly benefit patients undergoing stem cell transplantation by increasing resistance against viral infections and providing graft-vs.-leukemia (GVL) effects through enhanced cytolytic abilities. We tested the ability of a recently cloned stem cell factor, Flt3-ligand (Flt3L), in combination with interleukin-15 (IL-15), to stimulate CB mononuclear cells (MNCs) to proliferate and differentiate into NK cells, in comparison with adult peripheral blood (APB) MNCs. Unstimulated CB MNCs had low NK and lymphokine-activated killer (LAK) activity compared with APB MNCs. A similar dose-dependent increase in NK and LAK activity and CD16/56 expression was found with IL-15 in CB and APB MNCs after 10 days of culture. The NK cytotoxicity (against K562 cells) of IL-15-treated CB MNCs was lower than that of corresponding APB MNCs, while IL-15-induced LAK activity (against Daudi cells) of CB MNCs was comparable to that of corresponding APB MNCs. IL-15 resulted in greater CD16/56 expression in CB MNCs compared with APB MNCs after 10 days of culture. Flt3L, alone or in combination with IL-15, had little effect on CD16/56 expression and cytotoxicity. Cytotoxic activities and CD16/56 expression did not alter after CD34 depletion of CB MNCs. We therefore concluded that CB NK cells could be greatly activated and expanded with IL-15, but not with Flt3L. The greater expression of CD16/56 induced by IL-15 in CB MNCs may originate from non-CD34+ NK progenitor cells.

Adult↗

PubMed2000

Different forms of HSV-1 VP22a within purified virion and infected cells.

Utilizing the monoclonal antibody MCA406, our experimental data suggest that the herpes simplex virus type 1 (HSV-1) protein, VP22a, is present in the purified virus in a different form from that present within infected cells, namely the virion and infected-cell form, respectively. It seems reasonable to suggest that two different forms of VP22a are synthesized during the HSV-1 productive cycle. Using varying quantities of reducing agents, both inter- and intramolecular disulfide linkages were demonstrated in this protein family. Moreover, the VP22a-virion form could not be detected under nonreducing conditions by monoclonal antibody, even in the presence of proteolysis inhibitors, i.e. aprotinin, phenyl-methane-sulfonyl fluoride (PMSF) and soybean trypsin inhibitor. Varying temperature had little effect on the breakdown of VP22a disulfide bonds. A higher molecular-weight band, present in the nonreduced gel tracks, clearly indicates the presence of intermolecular disulfide bonds. Similarly, the appearance of bands of lower apparent molecular weight in the nonreduced tracks suggests the presence of intramolecular disulfide bonding. The VP22a infected-cell form may be modified to the virion form during the capsid-assembly process, prior to full capsid formation.

Animals↗

PubMed2000

[The development of an intelligent acoustic impedance middle ear analyzer].

This thesis introduces the measuring principle, device composition and main functions of an intelligent acoustic impedance middle ear analyzer. As well the results of clinical trial are analyzed in this paper. As an objective diagnostic method, aural acoustic impedance measuring device holds a very important position in diagnosing ear diseases and hearing obstacles.

Acoustic Impedance Tests↗

PubMed2000

Gastrointestinal manifestation and outcome of Henoch-Schonlein purpura in children.

BACKGROUND: We reviewed the clinical and laboratory manifestations and analyzed the outcome in children with Henoch-Schönlein purpura (HSP) and gastrointestinal involvement. METHODS: The medical records of 158 children who had Henoch-Schönlein purpura with gastrointestinal (GI) involvement admitted to our institution from June 1987 to December 1998 were reviewed. We retrospectively analyzed their demographic features, clinical manifestations, and outcome. RESULTS: Totally 104 boys and 54 girls (male: female = 1.9:1) were enrolled in this study, with a mean age of diagnosis of 5.8+/-4.8 years (range: 2 to 13 years). Sixty-three (40%) of our patients had preceding upper respiratory tract infection. The main GI manifestations included abdominal pain (88%); GI bleeding (75%), and vomiting (25%). Bowel edema was found in 71% of examined patients. Upper GI endoscopy provided supportive evidence of HSP in 58% of patients examined. Five patients were found to have marked jejunal edema with bowel collapse leading to severe intestinal obstruction. Thirteen patients (8.2%) had emergent complications including massive blood loss from GI tract in 4, seizure in 2, severe hypoalbuminemia in 2, and emergent surgical condition in 6. Twenty-one patients (13%) experienced prolonged hospitalization (> or =10 days). Bilious vomiting, hematemesis, leukocytosis (>20000/cmm), high C-reactive protein (>50 mg/l), and hemorrhagic erosive duodenitis were found to correlate with prolonged hospitalization. Fourteen (20%) of 70 patients who received follow-up for more than 5 years experienced GI recurrence of HSP. CONCLUSION: Despite severe and protracted GI symptoms in some HSP patients, the overall prognosis of GI involvement in children with HSP remains good.

Child↗

PubMed1999

Red wine inhibits monocyte chemotactic protein-1 expression and modestly reduces neointimal hyperplasia after balloon injury in cholesterol-Fed rabbits.

BACKGROUND: Wine consumption decreases the risk of myocardial infarction. Intimal hyperplasia contributes to restenosis after angioplasty. Local ethanol delivery inhibits intimal hyperplasia after balloon injury in rabbit iliac and pig coronary arteries. The effects of wine consumption on intimal response and monocyte chemotactic protein-1 (MCP-1) expression were studied in cholesterol-fed rabbits. METHODS AND RESULTS: Male rabbits were fed a 2% cholesterol diet together with red wine (12.5% vol, 5 mL/kg body wt per day; n=7), white wine (13.3% vol, 5 mL/kg body wt per day; n=7), or no wine as a control (n=8) for 6 weeks. A balloon injury of the abdominal aorta was performed at the end of the third week. Abdominal aortas were harvested at the end of 6 weeks. Neointimal hyperplasia was measured morphometrically. MCP-1 expression was determined by Northern blot, in situ hybridization, and immunohistochemistry. Rabbits fed red wine had significantly less neointimal hyperplasia than did control rabbits (intima/media area ratio 0.59+/-0.05 [red wine group] versus 0.79+/-0.07 [control group], P<0.05). However, rabbits fed white wine showed a trend (but not significant) toward less intimal response compared with control rabbits (intima/media area ratio 0.65+/-0.04 [white wine group] versus 0.79+/-0.07 [control group], P=0.165). Both red wine and white wine significantly reduced MCP-1 mRNA and protein expression in the aorta. CONCLUSIONS: Long-term consumption of red wine and white wine inhibits MCP-1 expression, and in the small number of animals studied, red wine modestly reduces neointimal hyperplasia. Since red wine exhibits higher antioxidant capacity than does white wine, the decreased intimal response might be partly attributed to its antioxidant effects.

Animals↗

PubMed1999

Weakly bound calcium ions involved in the thermostability of aqualysin I, a heat-stable subtilisin-type protease of Thermus aquaticus YT-1.

Aqualysin I is a heat-stable protease; in the presence of 1 mM Ca(2+), the enzyme is stable at 80 degrees C and shows the highest activity at the same temperature. After gel filtration to remove free Ca(2+) from the purified enzyme sample, the enzyme (holo-aqualysin I) still bound Ca(2+) (1 mol/mol of the enzyme), but was no longer stable at 80 degrees C. On treatment of the holo-enzyme with EDTA, bound Ca(2+) decreased to about 0.3 mol/mol of the enzyme. The thermostability of holo-aqualysin I was dependent on the concentration of added Ca(2+), and 1 mM added Ca(2+) stabilized the enzyme completely, suggesting that aqualysin I has at least two Ca(2+) binding sites, i.e. stronger and weaker binding ones. Titration calorimetry showed single binding of Ca(2+) to the holo-enzyme with an association constant of 3.1 x 10(3) M(-1), and DeltaH and TDeltaS were calculated to be 2.3 and 6.9 kcal/mol, respectively, at 13 degrees C. La(3+), Sr(2+), Nd(3+), and Tb(3+) stabilized the holo-enzyme at 80 degrees C, as Ca(2+) did. These results suggest that the weaker binding site exhibits structural flexibility to bind several metal cations different in size and valency, and that the metal binding to the weaker binding site is essential for the thermostability of aqualysin I.

Binding Sites↗