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1.
The tendon ruptures are serious injuries of the lover limb in middle age and physically active population. While the Achilles
tendon rupture is common, the patellar ligament and quadriceps ligament ruptures are an absolutely rare injury. Usually there
is no correlation between the velocity of the trauma and the supervening of the rupture. The aetiology of the degenerative
changes in the collagen structures of the tendons and ligaments which could be disposed for the rupture are still not clear.
Our hypothesis was that before the injury there are clear pathological abnormalities in the tissues of the tendons, which
are predisposed for the rupture, and could be monitored besides the classical histological methods by differential scanning
calorimetry. The thermal denaturation of human samples was monitored by a SETARAM Micro DSC-II calorimeter. All the experiments
were performed between 0 and 100 °C. The heating rate was 0.3 K/min. DSC scans clearly demonstrated significant differences
between the control and ruptured samples (control: T
m = 59.7 °C, T
1/2 = 1.4 °C and ΔH
cal = 8.54 J/g; ruptured Achilles tendon: T
m = 62.75 °C, T
1/2 = 2.6 °C and ΔH
cal = 1.54 J/g, ruptured Quadriceps tendon: T
m = 64.8 °C, T
1/2 = 1.6 °C and ΔH
cal = 1.53 J/g, ruptured Patellar tendon: T
m = 63.9 °C, T
1/2 = 1.41 °C and ΔH
cal = 0.97 J/g). These observations could be explained with the structural alterations caused by the biochemical processes. With
our investigations we could demonstrate that DSC is a useful and well applicable method for the investigation of collagen
tissue of the degenerated human tendons and ligaments. We can prove with this method that the degenerative changes of the
tissue elements increase the thermal stability of collagen tissues of the tendons which could be disposed for the rupture. 相似文献
2.
N. Wiegand L. Vámhidy B. Patczai E. Dömse P. Than L. Kereskai D. Lőrinczy 《Journal of Thermal Analysis and Calorimetry》2009,95(3):797-800
The Dupuytren contracture - degenerative shortening of the palmar aponeurosis - is a common disease of the hand in Europe.
The aetiology of the degenerative changes in the collagen structures is still not clear. To describe the clinical manifestation
of the disease we use an international classification according to Iselin. Our hypothesis was that in Dupuytren disease there
is a clear pathological abnormality in the tissue elements building up the palmar aponeurosis, which is responsible for the
disease, and could be monitored besides the classical histological methods by differential scanning calorimetry.
The thermal denaturation of different parts of human samples was monitored by a SETARAM Micro DSC-II calorimeter. All the
experiments were performed between 0 and 100°C. The heating rate was 0.3 K min−1. DSC scans clearly demonstrated significant differences between the different types and conditions of samples (control: T
m=63°C and ΔH
cal=4.1 J g−1, stage I.: T
m= 63°C and ΔH
cal=5.1 J g−1, stage II.: T
m=64°C and ΔH
cal=5.2 J g−1, stage III.: T
m=60°C and ΔH
cal=5.2 J g−1, stage IV.: T
m=60.2°C and ΔH
cal=5.3 J g−1). The heat capacity change between native and denatured states of aponeurosis samples increased with the degree of structural
alterations indicating significant water loosing. These observations could be explained with the structural alterations caused
by the biochemical processes.
With our investigations we could demonstrate that DSC is a useful and well applicable method for the investigation of collagen
tissue of the human aponeurosis. Our results may be of clinical relevance in the future i.e. in the choice of the optimal
time of surgical therapy of different clinical level Dupuytren contractures. 相似文献
3.
I. Naumov N. Wiegand B. Patczai L. Vámhidy D. Lőrinczy 《Journal of Thermal Analysis and Calorimetry》2012,108(1):59-65
The femoral neck fracture continues to be unsolved fractures and the guidelines for management are still evolving. The primary
complications arising from femoral neck fractures are non-union and avascular necrosis. The various methods currently available
for predicting the vascularity of the head at the time of fracture are not sufficiently quantitative to be used on a routine
clinical basis. The hypothesis was that after the femoral neck fracture there are clear pathological abnormalities in the
cartilage of the femoral head, which could be monitored besides the classical methods by differential scanning calorimetry.
The thermal denaturation of human samples was monitored by a SETARAM Micro DSC-II calorimeter. All the experiments were performed
between 0 and 100 °C. The heating rate was 0.3 K/min. DSC scans clearly demonstrated significant differences between the control
and different stages avascular samples (control, fresh fractures: T
m
= 68.2 °C, ΔH
cal = 2.87 J/g, avascular necrosis: T
m
= 70.7 °C, ΔH
cal = 3.61 J/g,). These observations could be explained with the structural alterations caused by the biochemical processes during
the degeneration of the cartilage due to avascular femoral head necrosis. With the investigations the authors could demonstrate
that DSC is a useful and well-applicable method for the investigation of hyaline cartilage of the fractured human femoral
head. It was confirmed significances between the changes of calorimetric results and the elapsed time from the primary femoral
neck fracture. 相似文献
4.
G. Bognár I. Szabó Cs. Pintér E. Ligeti D. Lőrinczy 《Journal of Thermal Analysis and Calorimetry》2010,102(1):65-68
Long head of the biceps (LHB) is an intra-articular tendon component of the shoulder joint. The function of this tendon is
complex. First, it is an origin of flexion in upper limb, and second it plays role in joint stabilisation during shoulder
movements. Histological type of tendon tissues is connective tissue. The mechanical behaviour of connective tissue is primarily
determined by the composition and organisation of collagens. In tendons, type I collagen is the principal structural element
of the extracellular matrix, which acts to transmit force between bones or bone and muscle. Owing to the special localisation
of this tendon, the intra-articular mechanical forces affect it to a considerable extent. The LHB is known as a source of
pain in pathologic states of the shoulder joint. The goal of this study was to establish the calorimetric standards of the
LHB in different ages, and to observe the changes of thermal properties of collagen during lifetime. LHB samples were taken
from 38 cadavers (between ages 0 and 90 years) without macroscopic sign of shoulder pathology. DSC analyses were performed
with SETARAM Micro DSC-II. The thermal denaturation parameters varied between T
m (°C): 57, ΔH (J/g): 0.26 (age: 0 year) and T
m (°C): 62.92, ΔH (J/g): 1.28 (age: 90 years). The ageing of collagenous tendon tissue can be clearly followed in changes of thermal denaturation
properties. The knowledge of the ageing of normal collagen provides a good basis to analyse further the LHB pathology. 相似文献
5.
1. Results of thermodynamic and kinetic investigations for the different crystalline calcium carbonate phases and their phase
transition data are reported and summarized (vaterite: V; aragonite: A; calcite: C). A→C: T
tr=455±10°C, Δtr
H=403±8 J mol–1 at T
tr, V→C: T
tr=320–460°C, depending on the way of preparation,Δtr
H=–3.2±0.1 kJ mol–1 at T
tr,Δtr
H=–3.4±0.9 kJ mol–1 at 40°C, S
V
Θ= 93.6±0.5 J (K mol)–1, A→C: E
A=370±10 kJ mol–1; XRD only, V→C: E
A=250±10 kJ mol–1; thermally activated, iso- and non-isothermal, XRD
2. Preliminary results on the preparation and investigation of inhibitor-free non-crystalline calcium carbonate (NCC) are
presented. NCC→C: T
tr=276±10°C,Δtr
H=–15.0±3 kJ mol–1 at T
tr, T
tr – transition temperature, Δtr
H – transition enthalpy, S
Θ – standard entropy, E
A – activation energy.
3. Biologically formed internal shell of Sepia officinalis seems to be composed of ca 96% aragonite and 4% non-crystalline calcium carbonate.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Pena R. Chauvet A. Masse J. Ribet J. P. Maurel J. L. 《Journal of Thermal Analysis and Calorimetry》1998,53(3):697-709
The phase diagram of R(+)-S(-) efaroxan hydrochloride (Tfus.(R)=245.1±0.3°C. ΔHfus.(R)=119.6±3.0 J g-1) shows a racemic compound. The melting temperature and melting enthalpy of the compound are: Tfus.(RS)=247.8±0.2°C and ΔHfus. (RS)=124.6±2.4 J g-1. A solid ↔ solid transformation takes place at Ttrs.=180±1°C, ΔHtrs.=15.0±0.4 J g-1. This transition is observed between 3 and 97% R(+). The stability of the racemic compound already established in a previous
study was confirmed by the value of Petterson's coefficient (i=1.19). The two eutectic positions at 20 and 80% R(+) that define
the range over which the racemic compound is found, exclude the use of resolution methods by preferential crystallization.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
G. Bognár Cs. Pintér B. Horváth T. Sydo E. Ligeti J. Pulai D. Lőrinczy 《Journal of Thermal Analysis and Calorimetry》2009,95(3):769-774
Osteonecrosis (ON) of the femoral frequently occurs after steroid medication. One of the final pathways leading to steroid
induced ON is thought to be pathologic fat metabolism. The pathobiological mechanism underlying the induction of fat metabolism
outslides by steroids leading to ON has not been fully elucidated. The purpose of this study was to examine the intraoperative
obtained gluteal fat tissue from ON patients with histology, gas chromatography (GC) and differential scanning calorimetry
(DSC) and to compare them with otherwise healthy patient’s samples. The histological sections showed no significant differences
compared with the control group. GC revealed that fraction of saturated fatty acids decreased in ON samples from mean values
of controls of 24% to 21, the polyunsaturated fraction from 20 to 14%. The monounsaturated acids showed an increase from mean
rate of 52% of the controls to 65% of steroid treated samples. DSC curves correlate with chromatographic analysis of the tissue
fatty acids (Steroid treated, heating between 0–100°C: T
m=5.7°C, ΔH= −15.8J/g−1; heating between −20–100°C: Tm= −9.96 and 5.85°C, ΔH= −59.17 and −16.2 J g−1. Non-necrotic, heating between 0–100°C: two separable transition with Tm=5.7 and 9.9°C, total ΔH= −20.8 J g−1; heating between −20–100°C: Tm= −10.9 and 4.95°C, total ΔH= −75.8 J g−1.)
Our preliminary findings are rather tendentious. Further investigations are needed with higher sample rate and under other
anamnestic circumstances too. 相似文献
8.
N. A. Halim Z. A. Ibrahim A. B. Ahmad 《Journal of Thermal Analysis and Calorimetry》2010,102(3):983-988
The high potential for intercalations by water and various guest molecules is induced by the exchangeable cation inside Ca2+–Montmorillonite gallery. XRD peak for Mon at 2θ = 6.04° (d
001 = 1.462 nm) shows the structural effect on the clay gallery influenced by the intercalated water layers. Further increases
in the gallery height are observed with the intercalation of octadecyl ammonium cations in OMON (d
001 = 1.840 nm) and ENR-50 matrix chains in CENR-50 (d
001 = 1.954 nm). DSC studies on the other hand reveal the thermal behaviors of intercalated molecules that are linked to the
exchangeable cations. The endothermic of Ca2+–Montmorillonite (H
Mon = 356.3 J/g) in low temperature range (30–100 °C) indicates the removal of free water and hydrogen bonded water molecules,
while the endothermic around 150 °C is related to the induced skeletal layer of water within Ca2+–Montmorillonite. The OMON endothermic (H
OMON = 47.0 J/g, T
m = 36.94 °C) tells that cation exchange had modified the water structures and content inside the renewed clay. The intercalation
of ENR-50 chains into OMON gallery reveals two endothermic with the T
m1 and T
m2 are at 86.24 and 113.80 °C, respectively. These T
ms confirm that the alkyl chain segment on octadecyl ammonium cation occupy the OMON interlayer space. 相似文献
9.
Ronaldo S. Nunes Felipe S. Semaan Alan T. Riga Éder T. G. Cavalheiro 《Journal of Thermal Analysis and Calorimetry》2009,97(1):349-353
The thermal properties of verapamil hydrochloride (VRP) and its physical association as binary mixtures with some common excipients
were evaluated. Thermogravimetry (TG) was used to determine the thermal mass loss, as well as to study the kinetics of VRP
thermal decomposition, using the Flynn-Wall-Ozawa model. Based on their frequent use in pharmacy, five different excipients
(microcrystalline cellulose, magnesium stearate, hydroxypropyl methylcellulose, polyvinylpyrrolidone and talc) were blended
with VRP. Samples were prepared by mixing the analyte and excipients in a proportion of 1:1 (m/m). DSC curves for pure VRP
presented an endothermic event at 143 ± 2 °C (ΔHmelt = 132 ± 4 J g−1), which corresponds to the melting (literature Tm = 143.7 °C, ΔHmelt = 130.6 J g−1). Comparisons among the observed results for each compound and their binary physical mixtures presented no relevant changes.
This suggests no interaction between the drug and excipient. 相似文献
10.
T. Sillinger P. Than B. Kocsis D. Lőrinczy 《Journal of Thermal Analysis and Calorimetry》2005,82(1):221-223
Summary Treatment of a bacterial arthritis is a challenging task for a clinician as inadequate therapy can cause cartilage destruction
and can result in severe osteoarthritis of the affected joint. The development of cartilage destruction in septic arthritis
is not known in details. The aim of this study was to follow this process by calorimetric method. We induced experimental
septic arthritis in knee joints of seven New Zealand rabbits by single inocculation of Staphylococcus aureusOKI 112001 culture (1.5 mL 8·108±5% c.f.u.). The first rabbit died on the 11thday. At that time all the other subjects were made overslept and samples were isolated from the cartilage of the femurs for
calorimetric measurement. The DSC scans clearly demonstrated the development of infective structural destruction in cartilage
from the first to the tenth day of incubation. In case of healthy control the melting temperatures (Tm) were: 49.7, 55 and 63.4°C and the total calorimetric enthalpy change (ΔH) was 0.55 J g-1. After the first day the enthalpy decreased (0.375 J g-1), the first two transition temperature shifted towards higher temperature: 57 and 63.15°C. Up to the fourth day the effect
of infection culminated with Tmof 49.3, 55.9, 59.4, 62.8°C and further decrease of the ΔH. At the fifth day the effect of infection is culminated in two separable thermal denaturation events (with 55 and 63.3°C
Tms) with high jump in ΔHindicating the dramatic change of the structure of rabbit cartilage, so this time elapsed seems to be critical from the point
of view of practical clinical relevance too. Between the 7thand 11thdays practically we had same melting temperatures (50 and 63°C) with low (~0.24 J g-1) enthalpy. 相似文献
11.
N. Wiegand I. Naumov L. G. Nőt L. Vámhidy D. Lőrinczy 《Journal of Thermal Analysis and Calorimetry》2013,111(3):1897-1902
Keloid and hypertrophic scarring is a dermal fibroproliferative disorder characterized by increased fibroblast proliferation and excessive production of collagen. Excess scar formation occurs after dermal injury as a result of abnormal wound healing. Keloid formation has been ascribed to altered growth factor regulation, aberrant collagen turnover, genetics, immune dysfunction, sebum reaction, and altered mechanics. No single hypothesis adequately explains keloid formation. The thermal denaturations of pathologic human skin scar tissues were monitored by a SETARAM Micro DSC-II calorimeter. All the experiments were performed between 0 and 100 °C. The heating rate was 0.3 K min?1. DSC scans clearly demonstrated significant differences between the different types and conditions of samples (intact skin: T m = 54.8 °C and ΔH cal = 4.5 J g?1; normal scar: T m = 53.8 °C and ΔH cal = 4.2 J g?1; hypertrophic scar: T m = 54.2 °C and ΔH cal = 2.4 J g?1; keloid: T m = 52.9 °C and ΔH cal = 8.3 J g?1). The heat capacity change between native and denatured states of samples increased with the degree of structural alterations indicating significant water loosing. These observations could be explained with the structural alterations caused by the biochemical processes. With our investigations, we could demonstrate that DSC is a useful and well-applicable method for the investigation of collagen tissue of the human keloid and hypertrophic scar tissues. Our results may be of clinical relevance in the future, i.e., in the diagnosis of the two different pathologic scar formations, or in the choice of the optimal therapy of the disease. 相似文献
12.
Humaira Farooqui Amena Mahmood Deeba S. Jairajpuri Faizan Ahmad Shakir Ali 《Journal of Thermal Analysis and Calorimetry》2011,104(1):339-342
Transition temperature and thermal stability of proteins were studied in the presence and absence of boron. The observed midpoint
of thermal denaturation (T
m) of cytochrome c (Cyt c) at pH 9.2 was 68.8 °C, which in the presence of boron increased to 71.0 °C. For metmyoglobin, T
m increased from 79.7 °C in the absence of boron to 83.5 °C in the presence of boron. Boron caused an increase of 10% in the
reversibility of thermal denaturation of cytochrome c when compared with control. Activity measurements of the heat treated proteins and T
m suggest an increased thermal stability toward inactivation and denaturation of heme proteins in the presence of boron. 相似文献
13.
The specific micro- and mesopore volumes (V) of alumina compacts fired between 900 and 1250 °C for 2 h were determined from nitrogen adsorption/desorption data. The
V value was taken as a sintering equilibrium parameter. An arbitrary sintering equilibrium constant (K
a) was estimated for each firing temperature by assuming K
a = (V
i − V)/V, where V
i is the largest value at 900 °C before sintering. Also, an arbitrary Gibbs energy (ΔG
a
°) of sintering was calculated for each temperature using the K
a value. The graph of ln K
a versus 1/T and ΔG
a
° versus T were plotted, and the real enthalpy (ΔH°) and the real entropy (ΔS°) of sintering were calculated from the slopes of the obtained straight lines, respectively. On the contrary, real ΔG° and K values were calculated using the real ΔH° and ΔS° values in the ΔG° = −RT lnK = 165814 − 124.7T relation in SI units. 相似文献
14.
Digo Hermínio P. Pinto Susana S. Moura Ramos Joaquim J. 《Journal of Thermal Analysis and Calorimetry》2004,77(3):893-904
The thermal behaviour of salicylsalicylic acid (CAS number 552-94-3) was studied by differential scanning calorimetry (DSC).
The endothermic melting peak and the fingerprint of the glass transition were characterised at a heating rate of 10°C min-1. The melting peak showed an onset at T
on = 144°C (417 K) and a maximum intensity at T
max = 152°C (425 K), while the onset of the glass transition signal was at T
on = 6°C. The melting enthalpy was found to be ΔmH = 28.9±0.3 kJ mol-1, and the heat capacity jump at the glass transition was ΔC
P = 108.1±0.1 J K-1mol-1. The study of the influence of the heating rate on the temperature location of the glass transition signal by DSC, allowed
the determination of the activation energy at the glass transition temperature (245 kJ mol-1), and the calculation of the fragility index of salicyl salicylate (m = 45). Finally, the standard molar enthalpy of formation of crystalline monoclinic salicylsalicylic acid at T = 298.15 K, was determined as ΔfHm
o(C14H10O5, cr) = - (837.6±3.3) kJ mol-1, by combustion calorimetry.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
Balázs Patczai Tibor Mintál László Gergely Nőt Norbert Wiegand Dénes Lőrinczy 《Journal of Thermal Analysis and Calorimetry》2017,127(2):1177-1180
Surgical techniques including new, possible resources to repair injured joints and damaged cartilage are still evolving. The exact effects of cryopreservation on the collected cartilage samples require accurate determination prior to utilization. The aim of our study was to analyze the impact of cryopreservation at ?80 °C on the structural properties of the human cartilage. The effects of storage time were also evaluated in conjunction with optimal utilization. The human cartilage samples were derived during operation and considered to be waste material. Samples were fresh frozen and stored at ?80 °C. Cryopreservation times were: 0, 1, 3, 6, and 12 weeks. To assess the biological and structural properties of the frozen human cartilage, we performed calorimetric examinations using differential scanning calorimetry (DSC). During the first 3 weeks, the calorimetric enthalpy (ΔH cal) showed an increasing tendency compared to controls, parallel with the denaturation temperature (T m): ΔH cal (J g?1) = 1.60 versus 2.49, T m1 (°C) = 61.73 versus 63.64. After the sixth week, both the enthalpy and the transition temperature decreased, compared to the control samples. The decrease in both the calorimetric enthalpy and T m could be explained by the decrease in bound water and the time-related degeneration in the structure of the cartilage. Here we found that the duration of cryopreservation interferes with the morphology of human cartilage samples only after 6 weeks of storage time. The thermal analyzes of human cartilage by DSC could be a useful method to follow the morphological changes in the clinical practice. 相似文献
16.
In this article, the enthalpy of dissolution for oxymatrine in 0.15 M citric acid solution is measured using a RD496-2000
Calvet Microcalorimeter at 36.5 °C under atmospheric pressure. The differential enthalpy (Δ
dif
H
m) and molar enthalpy (Δ
sol
H
m) were determined for oxymatrine dissolution in 0.15 M citric acid solution. On the basis of these experimental data and calculated
results, the kinetic equation, half-life, Δ
sol
H
m, Δ
sol
G
m, and Δ
sol
S
m of the dissolution process were also obtained. 相似文献
17.
Tandra?Das Biplab?K.?Bera Subhasis?Mallick Parnajyoti?Karmakar Arup?Mandal Subala?Mondal Gauri?S.?De Alak?K.?Ghosh 《Transition Metal Chemistry》2010,35(7):885-890
The interaction of thiosemicarbazide with the title complex has been studied spectrophotometrically in aqueous medium as a
function of [complex], [thiosemicarbazide], pH and temperature at constant ionic strength. At pH 7.4, the reaction shows two
distinct paths; both of which are [thiosemicarbazide] dependent. A parallel reaction scheme fits well with the experimental
findings. An associative interchange mechanism is proposed for both the paths; the activation parameters calculated from Eyring
plots are ΔH1≠ = 14.2 ± 0.8 kJ mol−1, ΔS1≠ = −241 ± 2 JK−1 mol−1, ΔH2≠ = 30.8 ± 1.4 kJ mol−1 and ΔS2≠ = −236 ± 4 JK−1 mol−1. From the temperature dependence of the outer sphere association complex equilibrium constants, the thermodynamic parameters
calculated are ΔH1° = 34.25 ± 1.9 kJ mol−1, ΔS1° = 146 ± 6 J K−1 mol−1 and ΔH2° = 9.4 ± 1.1 kJ mol−1, ΔS2° = 71 ± 3 JK−1 mol−1, which gives a negative ΔG° at all temperatures studied, supporting the spontaneous formation of an outer sphere association
complex. 相似文献
18.
J. N. Zhang Z. C. Tan Q. F. Meng Q. Shi B. Tong S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):461-467
The heat capacities (C
p,m) of 2-amino-5-methylpyridine (AMP) were measured by a precision automated adiabatic calorimeter over the temperature range
from 80 to 398 K. A solid-liquid phase transition was found in the range from 336 to 351 K with the peak heat capacity at
350.426 K. The melting temperature (T
m), the molar enthalpy (Δfus
H
m0), and the molar entropy (Δfus
S
m0) of fusion were determined to be 350.431±0.018 K, 18.108 kJ mol−1 and 51.676 J K−1 mol−1, respectively. The mole fraction purity of the sample used was determined to be 0.99734 through the Van’t Hoff equation.
The thermodynamic functions (H
T-H
298.15 and S
T-S
298.15) were calculated. The molar energy of combustion and the standard molar enthalpy of combustion were determined, ΔU
c(C6H8N2,cr)= −3500.15±1.51 kJ mol−1 and Δc
H
m0 (C6H8N2,cr)= −3502.64±1.51 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. The standard molar enthalpy of formation of the crystalline compound was derived, Δr
H
m0 (C6H8N2,cr)= −1.74±0.57 kJ mol−1. 相似文献
19.
E. Metwally A. Sh. Saleh S. M. Abdel-Wahaab H. A. El-Naggar 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(1):217-221
The diamide N,N,N′,N′-tetraoctyldiglycolamide (TODGA) was synthesized and characterized. The prepared TODGA was applied for extraction of Ce(III)
from nitric acid solutions. The equilibrium studies included the dependencies of cerium distribution ratio on nitric acid,
TODGA, nitrate ion, hydrogen ion and cerous ion concentrations. Analysis of the results indicates that the main extracted
species is Ce(TODGA)2(NO3)3HNO3. The capacity of Ce loading is approximately 45 mmol/L for 0.1 M solution of TODGA in n-hexane. Finally, the thermodynamic parameters were calculated: K (25 °C) = 3.8 × 103, ΔH = −36.7 ± 1.0 kJ/mol, ΔS = −54.6 ± 3.0 J/K mol, and ΔG = −20.4 ± 0.1 kJ/mol. 相似文献
20.
Javed MR Rashid MH Nadeem H Riaz M Perveen R 《Applied biochemistry and biotechnology》2009,157(3):483-497
Monomeric extracellular endoglucanase (25 kDa) of transgenic koji (Aspergillus oryzae cmc-1) produced under submerged growth condition (7.5 U mg−1 protein) was purified to homogeneity level by ammonium sulfate precipitation and various column chromatography on fast protein
liquid chromatography system. Activation energy for carboxymethylcellulose (CMC) hydrolysis was 3.32 kJ mol−1 at optimum temperature (55 °C), and its temperature quotient (Q
10) was 1.0. The enzyme was stable over a pH range of 4.1–5.3 and gave maximum activity at pH 4.4. V
max for CMC hydrolysis was 854 U mg−1 protein and K
m was 20 mg CMC ml−1. The turnover (k
cat) was 356 s−1. The pK
a1 and pK
a2 of ionisable groups of active site controlling V
max were 3.9 and 6.25, respectively. Thermodynamic parameters for CMC hydrolysis were as follows: ΔH* = 0.59 kJ mol−1, ΔG* = 64.57 kJ mol−1 and ΔS* = −195.05 J mol−1 K−1, respectively. Activation energy for irreversible inactivation ‘E
a(d)’ of the endoglucanase was 378 kJ mol−1, whereas enthalpy (ΔH*), Gibbs free energy (ΔG*) and entropy (ΔS*) of activation at 44 °C were 375.36 kJ mol−1, 111.36 kJ mol−1 and 833.06 J mol−1 K−1, respectively. 相似文献