scholarly journals Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

2019 ◽  
Vol 15 ◽  
pp. 137-144 ◽  
Author(s):  
Teresa Mena-Barragán ◽  
José L de Paz ◽  
Pedro M Nieto
Keyword(s):  
Chondroitin Sulfate ◽  
Exploratory Study ◽  
Glucuronic Acid ◽  
Building Blocks ◽  
Significant Loss ◽  
Efficient Synthesis ◽  
Substitution Pattern ◽  
The Impact

Here, we present an exploratory study on the fluorous-assisted synthesis of chondroitin sulfate (CS) oligosaccharides. Following this approach, a CS tetrasaccharide was prepared. However, in contrast to our previous results, a significant loss of β-selectivity was observed in [2 + 2] glycosylations involving N-trifluoroacetyl-protected D-galactosamine donors and D-glucuronic acid (GlcA) acceptors. These results, together with those obtained from experiments employing model monosaccharide building blocks, highlight the impact of the glycosyl acceptor structure on the stereoselectivity of glycosylation reactions. Our study provides useful data about the substitution pattern of GlcA units for the efficient synthesis of CS oligomers.

Effect of Glycosaminoglycans on Thrombin- and Atroxin-Induced Fibrin Assembly and Structure

1989 ◽  
Vol 62 (04) ◽  
pp. 1057-1061 ◽  
Author(s):  
Marcus E Carr ◽  
Patrick L Powers
Keyword(s):  
Chondroitin Sulfate ◽  
Fiber Diameter ◽  
Lag Phase ◽  
Low Molecular Weight ◽  
Fibrin Gels ◽  
Fiber Size ◽  
Induced Changes ◽  
The Impact ◽  
Fiber Radius ◽  
Turbidity Increase

SummaryThis study was performed to quantitate the impact of several glycosaminoglycans (GAG) on fibrin assembly and structure. Gel formation was monitored as the increase in optical density at 633 nm subsequent to thrombin (2 NIH u/ml) or atroxin (0.10 mg/ml) addition to solutions of buffered fibrinogen (1 mg/ml) or plasma. Gel absorbance was measured as a function of wavelength (400 to 800 nm) and gel fiber diameter and mass/length ratio (μ) were calculated. Chondroitin sulfate A (CSA)shortened the lag phase, enhanced the maximal rate of turbidity increase, and increased the final gel turbidity of fibrin gels formed by thrombin or atroxin. CSA (16 mg/ml) increased fiber μ from 1.3 to 3.1 × 1013 dalton/cm and fiber radius from 6.0 to 8.6 × 10-6 cm in thrombin-induced gels. μ increased from 0.7 to 2.7 × 1013 dalton/cm and fiber radius from 4 to 7.8 × 10-6 cm for atroxin-induced gels. Above 16 mg/ml, CSA caused fibrinogen precipitation in purified solutions but not in plasma. CSA inhibited thrombin-induced plasma clotting of plasma but effects in atroxin-mediated plasma gels paralleled those seen in purified solutions. Chondroitin sulfate B (CSB)-induced changes in fibrin were similar but slightly less dramatic than those seen with CSA. μ increased from 0.9 to 2.0 × 1013 dalton/cm for thrombin-induced fibrin gels and from 0.8 to 2.3 × 1013 dalton/cm for atroxininduced gels. Low molecular weight heparin (Mr = 5100) slowed fibrin assembly and reduced fiber size by 50% in thrombininduced gels. Changes in μ of atroxin-induced gels were much less pronounced (<20%). This study documents pronounced GAGinduced changes in fibrin structure which vary with GAG species and may mediate significant physiologic functions.

Mechanically-Tunable Quantum Interference in Ferrocene-Based Single-Molecule Junctions

2020 ◽  
Author(s):  
María Camarasa-Gómez ◽  
Daniel Hernangómez-Pérez ◽  
Michael S. Inkpen ◽  
Giacomo Lovat ◽  
E-Dean Fung ◽  
...  
Keyword(s):  
Single Molecule ◽  
Quantum Interference ◽  
Degrees Of Freedom ◽  
Building Blocks ◽  
Ferrocene Derivative ◽  
Single Molecule Junctions ◽  
Molecule Junction ◽  
Single Molecule Junction ◽  
The Impact ◽  
D Orbitals

Ferrocenes are ubiquitous organometallic building blocks that comprise a Fe atom sandwiched between two cyclopentadienyl (Cp) rings that rotate freely at room temperature. Of widespread interest in fundamental studies and real-world applications, they have also attracted<br>some interest as functional elements of molecular-scale devices. Here we investigate the impact of<br>the configurational degrees of freedom of a ferrocene derivative on its single-molecule junction<br>conductance. Measurements indicate that the conductance of the ferrocene derivative, which is<br>suppressed by two orders of magnitude as compared to a fully conjugated analog, can be modulated<br>by altering the junction configuration. Ab initio transport calculations show that the low conductance is a consequence of destructive quantum interference effects that arise from the hybridization of metal-based d-orbitals and the ligand-based π-system. By rotating the Cp rings, the hybridization, and thus the quantum interference, can be mechanically controlled, resulting in a conductance modulation that is seen experimentally.<br>

Model Pembelajaran Teams Games Tournaments (TGT) untuk Meningkatkan Hasil Belajar Siswa

2019 ◽  
Vol 3 (2) ◽  
pp. 110
Author(s):  
Suwarno Suwarno
Keyword(s):  
Social Capital ◽  
Academic Success ◽  
Service Learning ◽  
Learning Outcomes ◽  
School Effectiveness ◽  
Social Trust ◽  
Building Blocks ◽  
Learning Model ◽  
Committee Report ◽  
The Impact

<p><strong>A</strong><strong>bstract</strong><strong>. </strong>This study aims to determine the effectiveness of the Teams Games Tournament (TGT) learning model to improve student learning outcomes. This research is important because the lecture learning model makes learning meaningless so it impacts on low learning outcomes. This research uses quasi experiment using control class and experimental class. Respondents in this study were students of class X SMK 8 Semarang Academic Year 2017/2018. Sample selection using random sampling, class X1 is <em>used</em> as a control class and X2 is an experimental class. The experimental class was given an intervention by learning Teams Games Tournaments (TGT), while the control class used lecture learning. The effectiveness of the model was measured by the student test analysis method. then analyzed by completeness test and average difference test. The findings of this study are the learning outcomes of experimental class students achieving better learning outcomes than classes using the lecture method.</p><p><strong><em>Keywords</em></strong><em>: Learning Model, Teams Games Tournaments (TGT)</em><em>. Students</em></p><p><strong><br /></strong></p><p><strong>Daftar Pustaka</strong></p><p align="center"> </p><p>Bofota, Y. B., &amp; Bofota, Y. B. (2017). <em>The impact of social capital on children educational outcomes : the case of Tanzania The impact of social capital on children educational outcomes : The case of Tanzania</em>.</p><p>Cahuc, P., Shleifer, A., &amp; Algan, Y. (2014). <em>Teaching Practices and Social Capital</em>. (6052).</p><p>Catts, R., &amp; Ozga, J. (2015). <em>What is Social Capital and how might it be used in Scotland ’ s Schools ?</em> (36).</p><p>Flint, N. (2017). <em>Full report Schools , communities and social capital : building blocks in the ’ Big Society ’ Contents</em>.</p><p>Goddard, R. D. (2016). <em>Relational Networks , Social Trust , and Norms : A Social Capital Perspective on Students ’ Chances of Academic Success</em>. <em>25</em>(1), 59–74.</p><p>Eddy Prasongko, 2017. Team Game Tournament. Bandung. Jawa Barat</p><p>Endang Poerwanti, dkk. 2008. <em>Asesmen Pembelajaran SD.</em> Jakarta: Direktorat Jendral Pendidikan Tinggi Departemen Pendidikan Nasional</p><p>Hargreaves, A. (2015). <em>School Social Capital and School Effectiveness</em>. <em>37</em>, 119–136.</p><p>Kurnia, Inggridwati. dkk. 2018. <em>Perkembangan belajar peserta didik</em><em>.</em> Jakarta: Direktorat Jendral Pendidikan Tinggi Departemen Pendidikan Nasional</p><p>Purwanto. M Ngalim. 2015. <em>Psikologi Pendidikan</em>. Bandung: PT Remaja Rosdakarya</p><p>Siddiq, M. Djauhar. 2018. <em>Pengembangan Bahan Pembelajaran SD</em>. Jakarta: Direktorat Jendral Pendidikan Tinggi Departemen Pendidikan Nasional.</p><p>Sugiyono, 2005. Metode Penelitian Kuantitatif, Kualitatif dan Rn D, Bandung Aftabeta</p><p>Lash, D., &amp; Belfiore, G. (2017). <em>5 Essentials in Building Social Capital Report 4 of the MyWays Student Success Series</em>. (October).</p><p>Mikiewicz, P., Jonasson, J. T., Gudmundsson, G., Blondal, K. S., &amp; Korczewska, D. M. (2011). <em>Comparative research between Poland and Iceland</em>.</p><p>Schlesselman, L., Borrego, M., Bloom, T. J., Mehta, B., Drobitch, R. K., &amp; Smith, T. (2015). An Assessment Of Service-Learning In 34 US Schools Of Pharmacy Follow Up On The 2001 Professional Affairs Committee Report. <em>American Journal of Pharmaceutical Education</em>, <em>79</em>(8). https://doi.org/10.5688/ajpe798116</p><p><em><br /></em></p>

Development of Strategies for Glycopeptide Synthesis: An Overview on the Glycosidic Linkage

2020 ◽  
Vol 24 (21) ◽  
pp. 2475-2497
Author(s):  
Andrea Verónica Rodríguez-Mayor ◽  
German Jesid Peralta-Camacho ◽  
Karen Johanna Cárdenas-Martínez ◽  
Javier Eduardo García-Castañeda
Keyword(s):  
Chemical Synthesis ◽  
Solid Phase ◽  
Building Blocks ◽  
Heterogeneous Environments ◽  
Phase Synthesis ◽  
Low Concentrations ◽  
Biological Sources ◽  
Synthetic Routes ◽  
The Impact ◽  
Potential Use

Glycoproteins and glycopeptides are an interesting focus of research, because of their potential use as therapeutic agents, since they are related to carbohydrate-carbohydrate, carbohydrate-protein, and carbohydrate-lipid interactions, which are commonly involved in biological processes. It has been established that natural glycoconjugates could be an important source of templates for the design and development of molecules with therapeutic applications. However, isolating large quantities of glycoconjugates from biological sources with the required purity is extremely complex, because these molecules are found in heterogeneous environments and in very low concentrations. As an alternative to solving this problem, the chemical synthesis of glycoconjugates has been developed. In this context, several methods for the synthesis of glycopeptides in solution and/or solid-phase have been reported. In most of these methods, glycosylated amino acid derivatives are used as building blocks for both solution and solid-phase synthesis. The synthetic viability of glycoconjugates is a critical parameter for allowing their use as drugs to mitigate the impact of microbial resistance and/or cancer. However, the chemical synthesis of glycoconjugates is a challenge, because these molecules possess multiple reaction sites and have a very specific stereochemistry. Therefore, it is necessary to design and implement synthetic routes, which may involve various protection schemes but can be stereoselective, environmentally friendly, and high-yielding. This review focuses on glycopeptide synthesis by recapitulating the progress made over the last 15 years.

Motivation for the Pastoral Profession in the Netherlands

2000 ◽  
Vol 28 (2) ◽  
pp. 109-118 ◽  
Author(s):  
Hessel J. Zondag
Keyword(s):  
The Netherlands ◽  
Exploratory Study ◽  
Pastoral Ministry ◽  
Well Being ◽  
Organizational Psychology ◽  
Expectancy Theory ◽  
Way Of Life ◽  
Item Questionnaire ◽  
The Impact ◽  
Protestant Denominations

Expectancy theory has been utilized by organizational psychology to explore the expectations and valuations of individuals in various professions. This study employs expectancy theory to clergy, investigating pastors' personal motivations, or values, for assuming pastoral ministry and the subsequent expectation that these values will be honored by their activities within the pastorate. The responses of 235 pastors from Catholic and Protestant denominations on a 24-item questionnaire devised to gauge pastoral motivation and adapted to assess pastoral expectations were factor analyzed and correlated in this exploratory study. The analysis yielded four robust factors. The first two motives found to be dominant were the pursuit of a Christian Way of Life and Anthropocentric Altruism. Anthropocentric Egoism and Theocentric Egoism, although secondary motivations, were theoretically meaningful in the understanding of pastoral motivations and expectations. The impact of expectations upon pastoral well-being and resilience against burnout is discussed.

Marital Satisfaction of Portuguese Families in Times of Social Lockdown

2021 ◽  
pp. 106648072110098
Author(s):  
Carla Sílvia Fernandes ◽  
Bruno Magalhães ◽  
Sílvia Silva ◽  
Beatriz Edra
Keyword(s):  
Marital Satisfaction ◽  
Exploratory Study ◽  
Social Economic ◽  
Future Research ◽  
Marital Relations ◽  
The Social ◽  
The Family ◽  
Convenience Sampling ◽  
Global Threat ◽  
The Impact

The COVID-19 pandemic represents a global threat and crisis situation, and its wide-reaching impact has also affected marital satisfaction. Dysfunction of the marital system puts the survival of the family unit at risk. This research aimed to determine the level of marital satisfaction of Portuguese families during the social lockdown and the association between the variables under study. A descriptive, exploratory study was conducted. During the social lockdown, 276 people of Portuguese nationality and residing in Portugal were recruited using nonprobabilistic convenience sampling. Marital satisfaction in the pandemic phase showed low values that may be associated with the social, economic, and political context experienced by the pandemic situation. Future research must be carried out in order to identify, prevent, and intervene in situations of violence. In addition, future research should explore not only marital satisfaction during the current pandemic but a more systemic assessment of marital relations during crises, expanding the impact of marital satisfaction in family functioning.

scholarly journals Progress and challenges of implantable neural interfaces based on nature-derived materials

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Eugenio Redolfi Riva ◽  
Silvestro Micera
Keyword(s):  
Interface Design ◽  
Specific Area ◽  
Building Blocks ◽  
Matrix Proteins ◽  
Neural Interface ◽  
Neural Interfaces ◽  
Biomedical Science ◽  
Chronic Inflammatory Response ◽  
The Impact

AbstractNeural interfaces are bioelectronic devices capable of stimulating a population of neurons or nerve fascicles and recording electrical signals in a specific area. Despite their success in restoring sensory-motor functions in people with disabilities, their long-term exploitation is still limited by poor biocompatibility, mechanical mismatch between the device and neural tissue and the risk of a chronic inflammatory response upon implantation.In this context, the use of nature-derived materials can help address these issues. Examples of these materials, such as extracellular matrix proteins, peptides, lipids and polysaccharides, have been employed for decades in biomedical science. Their excellent biocompatibility, biodegradability in the absence of toxic compound release, physiochemical properties that are similar to those of human tissues and reduced immunogenicity make them outstanding candidates to improve neural interface biocompatibility and long-term implantation safety. The objective of this review is to highlight progress and challenges concerning the impact of nature-derived materials on neural interface design. The use of these materials as biocompatible coatings and as building blocks of insulation materials for use in implantable neural interfaces is discussed. Moreover, future perspectives are presented to show the increasingly important uses of these materials for neural interface fabrication and their possible use for other applications in the framework of neural engineering.

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