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Meisel Z, George S, Ahn S, Bazin D, Brown BA, Browne J, Carpino JF, Chung H, Cole AL, Cyburt RH, Estradé A, Famiano M, Gade A, Langer C, Matoš M, Mittig W, Montes F, Morrissey DJ, Pereira J, Schatz H, Schatz J, Scott M, Shapira D, Smith K, Stevens J, Tan W, Tarasov O, Towers S, Wimmer K, Winkelbauer JR, Yurkon J, Zegers RGT. Mass Measurement of 56Sc Reveals a Small A = 56 Odd-Even Mass Staggering, Implying a Cooler Accreted Neutron Star Crust. Phys Rev Lett 2015; 115:162501. [PMID: 26550869 DOI: 10.1103/physrevlett.115.162501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Indexed: 06/05/2023]
Abstract
We present the mass excesses of (52-57)Sc, obtained from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. The masses of 56Sc and 57Sc were determined for the first time with atomic mass excesses of -24.85(59)((-54)(+0)) MeV and -21.0(1.3) MeV, respectively, where the asymmetric uncertainty for 56Sc was included due to possible contamination from a long-lived isomer. The 56Sc mass indicates a small odd-even mass staggering in the A = 56 mass chain towards the neutron drip line, significantly deviating from trends predicted by the global FRDM mass model and favoring trends predicted by the UNEDF0 and UNEDF1 density functional calculations. Together with new shell-model calculations of the electron-capture strength function of 56Sc, our results strongly reduce uncertainties in model calculations of the heating and cooling at the 56Ti electron-capture layer in the outer crust of accreting neutron stars. We find that, in contrast to previous studies, neither strong neutrino cooling nor strong heating occurs in this layer. We conclude that Urca cooling in the outer crusts of accreting neutron stars that exhibit superbursts or high temperature steady-state burning, which are predicted to be rich in A≈56 nuclei, is considerably weaker than predicted. Urca cooling must instead be dominated by electron capture on the small amounts of adjacent odd-A nuclei contained in the superburst and high temperature steady-state burning ashes. This may explain the absence of strong crust Urca cooling inferred from the observed cooling light curve of the transiently accreting x-ray source MAXI J0556-332.
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Affiliation(s)
- Z Meisel
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
| | - S George
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
- Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany
| | - S Ahn
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
| | - D Bazin
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - B A Brown
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - J Browne
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
| | - J F Carpino
- Department of Physics, Western Michigan University, Kalamazoo, Michigan 49008, USA
| | - H Chung
- Department of Physics, Western Michigan University, Kalamazoo, Michigan 49008, USA
| | - A L Cole
- Physics Department, Kalamazoo College, Kalamazoo, Michigan 49006, USA
| | - R H Cyburt
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
| | - A Estradé
- School of Physics and Astronomy, The University of Edinburgh, EH8 9YL Edinburgh, United Kingdom
| | - M Famiano
- Department of Physics, Western Michigan University, Kalamazoo, Michigan 49008, USA
| | - A Gade
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - C Langer
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
| | - M Matoš
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - W Mittig
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - F Montes
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
| | - D J Morrissey
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - J Pereira
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
| | - H Schatz
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
| | - J Schatz
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - M Scott
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - D Shapira
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - K Smith
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - J Stevens
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
| | - W Tan
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - O Tarasov
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - S Towers
- Department of Physics, Western Michigan University, Kalamazoo, Michigan 49008, USA
| | - K Wimmer
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - J R Winkelbauer
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - J Yurkon
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - R G T Zegers
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
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Noji S, Zegers RGT, Austin SM, Baugher T, Bazin D, Brown BA, Campbell CM, Cole AL, Doster HJ, Gade A, Guess CJ, Gupta S, Hitt GW, Langer C, Lipschutz S, Lunderberg E, Meharchand R, Meisel Z, Perdikakis G, Pereira J, Recchia F, Schatz H, Scott M, Stroberg SR, Sullivan C, Valdez L, Walz C, Weisshaar D, Williams SJ, Wimmer K. β+ Gamow-Teller transition strengths from 46Ti and stellar electron-capture rates. Phys Rev Lett 2014; 112:252501. [PMID: 25014806 DOI: 10.1103/physrevlett.112.252501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Indexed: 06/03/2023]
Abstract
The Gamow-Teller strength in the β(+) direction to (46)Sc was extracted via the (46)Ti(t,(3)He + γ) reaction at 115 MeV/u. The γ-ray coincidences served to precisely measure the very weak Gamow-Teller transition to a final state at 991 keV. Although this transition is weak, it is crucial for accurately estimating electron-capture rates in astrophysical scenarios with relatively low stellar densities and temperatures, such as presupernova stellar evolution. Shell-model calculations with different effective interactions in the pf shell-model space do not reproduce the experimental Gamow-Teller strengths, which is likely due to sd-shell admixtures. Calculations in the quasiparticle random phase approximation that are often used in astrophysical simulations also fail to reproduce the experimental Gamow-Teller strength distribution, leading to strongly overestimated electron-capture rates. Because reliable theoretical predictions of Gamow-Teller strengths are important for providing astrophysical electron-capture reaction rates for a broad set of nuclei in the lower pf shell, we conclude that further theoretical improvements are required to match astrophysical needs.
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Affiliation(s)
- S Noji
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
| | - R G T Zegers
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - Sam M Austin
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - T Baugher
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - D Bazin
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - B A Brown
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - C M Campbell
- Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - A L Cole
- Physics Department, Kalamazoo College, Kalamazoo, Michigan 49006, USA
| | - H J Doster
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - A Gade
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - C J Guess
- Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, Massachusetts 01854, USA and Department of Physics and Astronomy, Rowan University, Glassboro, New Jersey 08028, USA
| | - S Gupta
- Indian Institute of Technology Ropar, Nangal Road, Rupnagar, Punjab 140001, India
| | - G W Hitt
- Department of Applied Mathematics and Sciences, Khalifa University of Science, Technology, and Research, P.O. Box 127788 Abu Dhabi, UAE
| | - C Langer
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA
| | - S Lipschutz
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - E Lunderberg
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - R Meharchand
- Neutron and Nuclear Science Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Z Meisel
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - G Perdikakis
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics, Central Michigan University, Mt. Pleasant, Michigan 48859, USA
| | - J Pereira
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - F Recchia
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - H Schatz
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - M Scott
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - S R Stroberg
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - C Sullivan
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - L Valdez
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - C Walz
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - D Weisshaar
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - S J Williams
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - K Wimmer
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA and Department of Physics, Central Michigan University, Mt. Pleasant, Michigan 48859, USA
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Sasano M, Perdikakis G, Zegers RGT, Austin SM, Bazin D, Brown BA, Caesar C, Cole AL, Deaven JM, Ferrante N, Guess CJ, Hitt GW, Meharchand R, Montes F, Palardy J, Prinke A, Riley LA, Sakai H, Scott M, Stolz A, Valdez L, Yako K. Gamow-Teller transition strengths from 56Ni. Phys Rev Lett 2011; 107:202501. [PMID: 22181727 DOI: 10.1103/physrevlett.107.202501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Indexed: 05/31/2023]
Abstract
A new technique to measure (p,n) charge-exchange reactions in inverse kinematics at intermediate energies on unstable isotopes was successfully developed and used to study the (56)Ni(p,n) reaction at 110 MeV/u. Gamow-Teller transition strengths from (56)Ni leading to (56)Cu were obtained and compared with shell-model predictions in the pf shell using the KB3G and GXPF1A interactions. The calculations with the GXPF1A interaction reproduce the experimental strength distribution much better than the calculations that employed the KB3G interaction, indicating deficiencies in the spin-orbit and proton-neutron residual potentials for the latter. The results are important for improving the description of electron-capture rates on nuclei in the iron region, which are important for modeling the late evolution of core-collapse and thermonuclear supernovae.
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Affiliation(s)
- M Sasano
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, 48824-1321, USA
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Cole AL, Lee PJ, Hughes DA, Deegan PB, Waldek S, Lachmann RH. Depression in adults with Fabry disease: a common and under-diagnosed problem. J Inherit Metab Dis 2007; 30:943-51. [PMID: 17994284 DOI: 10.1007/s10545-007-0708-6] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Revised: 08/20/2007] [Accepted: 09/20/2007] [Indexed: 11/29/2022]
Abstract
BACKGROUND Anderson-Fabry disease (AFD), an X-linked lysosomal storage disorder, leads to multi-organ dysfunction and premature mortality. Depression in adults with AFD has been reported, but no large study has been done. We have examined the adult Fabry population in the United Kingdom to describe the prevalence, associated factors and frequency of diagnosis of depression. METHODS Postal questionnaires were sent from four adult clinics to 296 AFD patients. A response rate of 62% (n = 184; 74 male, 110 female) formed the data set. Questionnaires collected demographic and Fabry-specific information. Depression status was assessed using the Centre for Epidemiological Studies depression scale (CES-D). RESULTS Responders were aged between 18 and 76 years (mean 44). The prevalence of depression was 46%, of which 28% were consistent with 'severe clinical depression'. Unlike the normal population, males with AFD report a higher prevalence of severe depression than females (36% males; 22% females). Interference of AFD symptoms with individuals' lives (particularly acroparaesthesiae or anhidrosis) showed the largest odds of association with depression. Relationship and financial status proved strong predictors of depression: 88% of those with mild-moderate depression and 72% with severe depression were undiagnosed. CONCLUSION Depression is common and under-diagnosed in AFD. Proper assessment of and treatment for depression could improve the quality of life of these patients.
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Affiliation(s)
- A L Cole
- Charles Dent Metabolic Unit, Box 92, The National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N3BG, UK.
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Clement RRC, Bazin D, Benenson W, Brown BA, Cole AL, Cooper MW, DeYoung PA, Estrade A, Famiano MA, Frank NH, Gade A, Glasmacher T, Hosmer PT, Lynch WG, Montes F, Mueller WF, Peaslee GF, Santi P, Schatz H, Sherrill BM, van Goethem MJ, Wallace MS. New approach for measuring properties of rp-process nuclei. Phys Rev Lett 2004; 92:172502. [PMID: 15169141 DOI: 10.1103/physrevlett.92.172502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2003] [Indexed: 05/24/2023]
Abstract
A new experimental approach was developed that can reduce the uncertainties in astrophysical rapid proton capture (rp) process calculations due to nuclear data. This approach utilizes neutron removal from a radioactive ion beam to populate the nuclear states of interest. Excited states were deduced by the gamma-decay spectra measured in a semiconductor Ge-detector array. In the first case studied, 33Ar, excited states were measured with uncertainties of several keV. The 2 orders of magnitude improvement in the uncertainty of the level energies resulted in a 3 orders of magnitude improvement in the uncertainty of the calculated 32Cl(p,gamma)33Ar rate that is critical to the modeling of the rp process. This approach has the potential to measure key properties of almost all interesting nuclei on the rp-process path.
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Affiliation(s)
- R R C Clement
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA.
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Abstract
Fabry disease patients have increased risk of vascular disease despite cardioprotective increased HDL-cholesterol. Enzyme therapy does not significantly alter the lipid profile in the short term.
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Affiliation(s)
- D J Cartwright
- Charles Dent Metabolic Unit, National Hospital for Neurology and Neurosurgery, London, UK
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Muir AD, Cole AL, Walker JR. Antibiotic compounds from New Zealand plants. I. Falcarindiol, an anti-dermatophyte agent from Schefflera digitata. Planta Med 1982; 44:129-133. [PMID: 7089093 DOI: 10.1055/s-2007-971421] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
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McCallion RF, Cole AL, Walker JR, Blunt JW, Munro MH. Antibiotic substances from New Zealand plants. II. Polygodial, an anti-Candida agent from Pseudowintera colorata. Planta Med 1982; 44:134-138. [PMID: 7089094 DOI: 10.1055/s-2007-971422] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
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Shepherd MG, Tong CC, Cole AL. Substrate specificity and mode of action of the cellulases from the thermophilic fungus Thermoascus aurantiacus. Biochem J 1981; 193:67-74. [PMID: 6796043 PMCID: PMC1162576 DOI: 10.1042/bj1930067] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The substrate specificities of three cellulases and a beta-glucosidase purified from Thermoascus aurantiacus were examined. All three cellulases partially degraded native cellulose. Cellulase I, but not cellulase II and cellulase III, readily hydrolyzed the mixed beta-1,3; beta-1,6-polysaccharides such as carboxymethyl-pachyman, yeast glucan and laminarin. Both cellulase I and the beta-glucosidase degraded xylan, and it is proposed that the xylanase activity is an inherent feature of these two enzymes. Lichenin (beta-1,4; beta-1,3) was degraded by all three cellulases. Cellulase II cannot degrade carboxymethyl-cellulose, and with filter paper as substrate the end product was cellobiose, which indicates that cellulase II is an exo-beta-1,4-glucan cellobiosylhydrolase. Degradation of cellulose (filter paper) can be catalysed independently by each of the three cellulases; there was no synergistic effect between any of the cellulases, and cellobiose was the principal product of degradation. The mode of action of one cellulase (cellulase III) was examined by using reduced cellulodextrins. The central linkages of the cellulodextrins were the preferred points of cleavage, which, with the rapid decrease in viscosity of carboxymethyl-cellulose, confirmed that cellulase III was an endocellulase. The rate of hydrolysis increased with chain length of the reduced cellulodextrins, and these kinetic data indicated that the specificity region of cellulase III was five or six glucose units in length.
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Abstract
Three cellulases and a beta-glucosidase were purified from the culture filtrate of the thermophilic fungus Thermoascus aurantiacus. The isolated enzymes were all homogeneous on polyacrylamide-disc-gel electrophoresis. Data from chromatography on Bio-Gel P-60 and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis indicated mol.wts. of 87000 (beta-glucosidase), 78000 (cellulase I), 49000 (cellulase II) and 34000 (cellulase III); the carbohydrate contents of the enzymes were 33.0, 5.5, 2.6 and 1.8% (w/w) respectively. Although the three purified cellulases were active towards filter paper, only cellulases I and III were active towards CM(carboxymethyl)-cellulose. Cellulase I was also active towards yeast glucan. The Km and catalytic-centre-activity values for the enzymes were as follows; 0.52 mumol/ml and 6.5 X 10(4) for beta-glucosidase on p-nitrophenyl beta-D-glucoside, 3.9 mg/ml and 6.3 for cellulase I on CM-cellulose, 1.2 mg/ml and 1.1 for cellulase I on yeast glucan, 35.5 mg/ml and 0.34 for cellulase II on filter paper, and 1.9 mg/ml and 33 for cellulase III on CM-cellulose.
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