scholarly journals Direct Assessment of the α-Helix Nucleation Time

2011 ◽  
Vol 115 (22) ◽  
pp. 7472-7478 ◽  
Author(s):  
Arnaldo L. Serrano ◽  
Matthew J. Tucker ◽  
Feng Gai
Keyword(s):  
Nucleation Time ◽  
Direct Assessment ◽  
Helix Nucleation ◽  
Α Helix

scholarly journals Helix Nucleation by the Smallest Known α-Helix in Water

2016 ◽  
Vol 55 (29) ◽  
pp. 8275-8279 ◽  
Author(s):  
Huy N. Hoang ◽  
Russell W. Driver ◽  
Renée L. Beyer ◽  
Timothy A. Hill ◽  
Aline D. de Araujo ◽  
...  
Keyword(s):  
Helix Nucleation ◽  
Α Helix

α-Helix Nucleation Constant in Copolypeptides of Alanine and Ornithine or Lysine

1998 ◽  
Vol 120 (41) ◽  
pp. 10646-10652 ◽  
Author(s):  
Jianxin Yang ◽  
Kang Zhao ◽  
Youxiang Gong ◽  
Alexander Vologodskii ◽  
Neville R. Kallenbach
Keyword(s):  
Helix Nucleation ◽  
Α Helix

What Is the Time Scale for α-Helix Nucleation?

2011 ◽  
Vol 133 (17) ◽  
pp. 6809-6816 ◽  
Author(s):  
David De Sancho ◽  
Robert B. Best
Keyword(s):  
Time Scale ◽  
Helix Nucleation ◽  
Α Helix

scholarly journals Helix Nucleation by the Smallest Known α-Helix in Water

2016 ◽  
Vol 128 (29) ◽  
pp. 8415-8419 ◽  
Author(s):  
Huy N. Hoang ◽  
Russell W. Driver ◽  
Renée L. Beyer ◽  
Timothy A. Hill ◽  
Aline D. de Araujo ◽  
...  
Keyword(s):  
Helix Nucleation ◽  
Α Helix

Assessment of Cognitive Load in Multimedia Learning Using Dual-Task Methodology

2002 ◽  
Vol 49 (2) ◽  
pp. 109-119 ◽  
Author(s):  
Roland Brünken ◽  
Susan Steinbacher ◽  
Jan L. Plass ◽  
Detlev Leutner
Keyword(s):  
Cognitive Load ◽  
Dual Task ◽  
Cognitive Load Theory ◽  
Multimedia Learning ◽  
Learning Systems ◽  
Learning Materials ◽  
New Approach ◽  
Direct Assessment ◽  
Load Theory ◽  
Audiovisual Presentation

Abstract. In two pilot experiments, a new approach for the direct assessment of cognitive load during multimedia learning was tested that uses dual-task methodology. Using this approach, we obtained the same pattern of cognitive load as predicted by cognitive load theory when applied to multimedia learning: The audiovisual presentation of text-based and picture-based learning materials induced less cognitive load than the visual-only presentation of the same material. The findings confirm the utility of dual-task methodology as a promising approach for the assessment of cognitive load induced by complex multimedia learning systems.

Development of an IRT-based Direct Assessment of Preschool Science

2008 ◽  
Author(s):  
Daryl B. Greenfield ◽  
Ximena Dominguez ◽  
Janna Marie Fuccillo ◽  
Michelle Filomena Maier ◽  
Ariela Caren Greenberg
Keyword(s):  
Direct Assessment ◽  
Preschool Science

Direct Assessment of Functional Status Scale

1989 ◽  
Author(s):  
David A. Loewenstein ◽  
Ellen Amigo ◽  
Ranjan Duara ◽  
Andrew Guterman ◽  
Deborah Hurwitz ◽  
...  
Keyword(s):  
Functional Status ◽  
Direct Assessment

Effect of Temperature and pH on the Secondary Structure and Denaturation Process of Jumbo Squid Hepatopancreas Cathepsin D.

2019 ◽  
Vol 26 (7) ◽  
pp. 532-541 ◽  
Author(s):  
Cadena-Cadena Francisco ◽  
Cárdenas-López José Luis ◽  
Ezquerra-Brauer Josafat Marina ◽  
Cinco-Moroyoqui Francisco Javier ◽  
López-Zavala Alonso Alexis ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Secondary Structure ◽  
Cathepsin D ◽  
Thermal Denaturation ◽  
Protein Denaturation ◽  
Marine Organisms ◽  
Effect Of Temperature ◽  
Jumbo Squid ◽  
Α Helix ◽  
Circular Dichroïsm

Background: Cathepsin D is a lysosomal enzyme that is found in all organisms acting in protein turnover, in humans it is present in some types of carcinomas, and it has a high activity in Parkinson's disease and a low activity in Alzheimer disease. In marine organisms, most of the research has been limited to corroborate the presence of this enzyme. It is known that cathepsin D of some marine organisms has a low thermostability and that it has the ability to have activity at very acidic pH. Cathepsin D of the Jumbo squid (Dosidicus gigas) hepatopancreas was purified and partially characterized. The secondary structure of these enzymes is highly conserved so the role of temperature and pH in the secondary structure and in protein denaturation is of great importance in the study of enzymes. The secondary structure of cathepsin D from jumbo squid hepatopancreas was determined by means of circular dichroism spectroscopy. Objective: In this article, our purpose was to determine the secondary structure of the enzyme and how it is affected by subjecting it to different temperature and pH conditions. Methods: Circular dichroism technique was used to measure the modifications of the secondary structure of cathepsin D when subjected to different treatments. The methodology consisted in dissecting the hepatopancreas of squid and freeze drying it. Then a crude extract was prepared by mixing 1: 1 hepatopancreas with assay buffer, the purification was in two steps; the first step consisted of using an ultrafiltration membrane with a molecular cut of 50 kDa, and the second step, a pepstatin agarose resin was used to purification the enzyme. Once the enzyme was purified, the purity was corroborated with SDS PAGE electrophoresis, isoelectric point and zymogram. Circular dichroism is carried out by placing the sample with a concentration of 0.125 mg / mL in a 3 mL quartz cell. The results were obtained in mdeg (millidegrees) and transformed to mean ellipticity per residue, using 111 g/mol molecular weight/residue as average. Secondary-structure estimation from the far-UV CD spectra was calculated using K2D Dichroweb software. Results: It was found that α helix decreases at temperatures above 50 °C and above pH 4. Heating the enzyme above 70°C maintains a low percentage of α helix and increases β sheet. Far-UV CD measurements of cathepsin D showed irreversible thermal denaturation. The process was strongly dependent on the heating rate, accompanied by a process of oligomerization of the protein that appears when the sample is heated, and maintained a certain time at this temperature. An amount typically between 3 and 4% α helix of their secondary structure remains unchanged. It is consistent with an unfolding process kinetically controlled due to the presence of an irreversible reaction. The secondary structure depends on pH, and a pH above 4 causes α helix structures to be modified. Conclusion: In conclusion, cathepsin D from jumbo squid hepatopancreas showed retaining up to 4% α helix at 80°C. The thermal denaturation of cathepsin D at pH 3.5 is under kinetic control and follows an irreversible model.

The Inhibition of Polysialyltranseferase ST8SiaIV Through Heparin Binding to Polysialyltransferase Domain (PSTD)

2019 ◽  
Vol 15 (5) ◽  
pp. 486-495 ◽  
Author(s):  
Li-Xin Peng ◽  
Xue-Hui Liu ◽  
Bo Lu ◽  
Si-Ming Liao ◽  
Feng Zhou ◽  
...  
Keyword(s):  
Fluorescence Quenching ◽  
Polysialic Acid ◽  
Neuronal Cell ◽  
Cd Spectroscopy ◽  
Migration And Invasion ◽  
Heparin Binding ◽  
Clinical Prognosis ◽  
Quenching Analysis ◽  
Different Types ◽  
Α Helix

Background:The polysialic acid (polySia) is a unique carbohydrate polymer produced on the surface Of Neuronal Cell Adhesion Molecule (NCAM) in a number of cancer cells, and strongly correlates with the migration and invasion of tumor cells and with aggressive, metastatic disease and poor clinical prognosis in the clinic. Its synthesis is catalyzed by two polysialyltransferases (polySTs), ST8SiaIV (PST) and ST8SiaII (STX). Selective inhibition of polySTs, therefore, presents a therapeutic opportunity to inhibit tumor invasion and metastasis due to NCAM polysialylation. Heparin has been found to be effective in inhibiting the ST8Sia IV activity, but no clear molecular rationale. It has been found that polysialyltransferase domain (PSTD) in polyST plays a significant role in influencing polyST activity, and thus it is critical for NCAM polysialylation based on the previous studies.Objective:To determine whether the three different types of heparin (unfractionated hepain (UFH), low molecular heparin (LMWH) and heparin tetrasaccharide (DP4)) is bound to the PSTD; and if so, what are the critical residues of the PSTD for these binding complexes?Methods:Fluorescence quenching analysis, the Circular Dichroism (CD) spectroscopy, and NMR spectroscopy were used to determine and analyze interactions of PSTD-UFH, PSTD-LMWH, and PSTD-DP4.Results:The fluorescence quenching analysis indicates that the PSTD-UFH binding is the strongest and the PSTD-DP4 binding is the weakest among these three types of the binding; the CD spectra showed that mainly the PSTD-heparin interactions caused a reduction in signal intensity but not marked decrease in α-helix content; the NMR data of the PSTD-DP4 and the PSTDLMWH interactions showed that the different types of heparin shared 12 common binding sites at N247, V251, R252, T253, S257, R265, Y267, W268, L269, V273, I275, and K276, which were mainly distributed in the long α-helix of the PSTD and the short 3-residue loop of the C-terminal PSTD. In addition, three residues K246, K250 and A254 were bound to the LMWH, but not to DP4. This suggests that the PSTD-LMWH binding is stronger than the PSTD-DP4 binding, and the LMWH is a more effective inhibitor than DP4.Conclusion:The findings in the present study demonstrate that PSTD domain is a potential target of heparin and may provide new insights into the molecular rationale of heparin-inhibiting NCAM polysialylation.

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