49 research outputs found
The solution structure of the human IgG2 subclass is distinct from those for human IgG1 and IgG4 providing an explanation for their discrete functions
No full textHuman IgG2 antibody displays distinct therapeutically-useful properties compared with the IgG1, IgG3 and IgG4 antibody subclasses. IgG2 is the second most abundant IgG subclass, being able to bind human FcγRII/FcγRIII, but not to FcγRI or complement C1q. Structural information on IgG2 is limited by the absence of a full-length crystal structure for this. To this end, we determined the solution structure of human myeloma IgG2 by atomistic X-ray and neutron scattering modelling. Analytical ultracentrifugation disclosed that IgG2 is monomeric with a sedimentation coefficient s020,w of 7.2 S. IgG2 dimer formation was ≤ 5% and independent of the buffer conditions. Small-angle X-ray scattering in a range of NaCl concentrations and in light and heavy water revealed that the X-ray radius of gyration Rg is 5.2-5.4 nm, after allowing for radiation damage at higher concentrations, and that the neutron Rg value of 5.0 nm remained unchanged in all conditions. The X-ray and neutron distance distribution curves P(r) revealed two peaks, M1 and M2, that were unchanged in different buffers. The creation of ˃123,000 physically-realistic atomistic models by Monte Carlo simulations for joint X-ray and neutron-scattering curve fits, constrained by the requirement of correct disulfide bridges in the hinge, resulted in the determination of symmetric Y-shaped IgG2 structures. These molecular structures were distinct from those for asymmetric IgG1 and asymmetric and symmetric IgG4, and were attributable to the four hinge disulfides. Our IgG2 structures rationalize the existence of the human IgG1, IgG2, and IgG4 subclasses, and explain the receptor binding functions of IgG2
Unravelling the interaction of the human IgG subclasses with their ligands using biophysical methods
No full textAntibodies are responsible for binding to antigens through their Fab arms and eliciting an immune response by binding to Fcγ receptors (FcγR). IgG4 is associated with IgG4-related disease. Human IgG in blood consists of four subclasses (IgG1, IgG2, IgG3 and IgG4). In order to identify their solution structures, monoclonal IgG1 and IgG4 and myeloma IgG2 were studied using analytical ultracentrifugation (AUC) and small-angle X-ray and neutron scattering (SAXS, SANS), followed by atomistic modelling using molecular dynamics and Monte Carlo methods. The three IgG subclasses exhibit variable conformations and flexibility, reflecting their function. FcγRI (CD64) is the sole high-affinity human IgG receptor. Its crystal structure showed that its three domains D1, D2 and D3 form a compact “seahorse” shape. To identify its solution structure, AUC and SAXS data and their modelling showed that FcγRI is more elongated than its crystal structure, in which the D1 and D2 domains were no longer in contact with each other, and the D3 domain showed flexibility. The solution structures of the IgG1 and IgG4 complexes with FcγRI were determined by AUC, SAXS and SANS. These showed a 1:1 binding stoichiometry. Their atomistic modelling showed that the Fc region in IgG1/IgG4 accommodates one FcγRI asymmetrically, and the two Fab arms were displaced to enable FcγRI binding. The modelling showed that the bound FcγRI changed conformation back into a compact “seahorse” where D1 is folded back against the D2 domain. Here, the solution structure of full-length IgG with FcγRI resembled the crystal structures of the IgG Fc fragment complexes with FcγRI. It was concluded that the folding back of FcγRI into a “seahorse” conformation ensures 1:1 binding and high-affinity interaction, giving an effective and regulated immune response to remove foreign antigens. This thesis furthers our understanding of the conformations of human IgG and their association with disease
Web-based English comprehension question analysis and recommendation system
No full textPrimary School Leaving Examination (PSLE) is the most important examination for Primary Six students. One of the core subjects, English, is the most widely mode of language both spoken and written in Singapore. Therefore it is of paramount important that the students can communicate effectively using it and become independent lifelong learners.
However due to the heavy workload and limited time that current students encountered led to students trying to find a more efficient way to revise and reinforce their learning method to better suit their current learning ability. Nevertheless, there is still an absence of studying technique that tailor to each individual student’s learning ability.
This project aims to develop and build an English Comprehension Knowledge System which will aid student in better prepare for their English examination. The author focused primarily on comprehension which includes Graphic Stimulus, Open-Ended, Closed-Ended and Comprehension Cloze, which holds a substantial percentage in the examination. With the increasing amount of technology used, the system will be web based providing numerous features like viewing, practicing and analyzing of questions. In order to overcome the above challenges, the author emphasize on two approaches, Computerized Adaptive Testing (CAT) and Test Paper Generation (TPG) techniques.
In conclusion, through the use of the system, the author hope that it will help enhance the quality of learning from the result of practicing questions that are in line with each student’s capability therefore achieving better grades.Bachelor of Engineering (Computer Science
The solution structure of the unbound IgG Fc receptor CD64 resembles its crystal structure:Implications for function
No full textFcγRI (CD64) is the only high-affinity Fcγ receptor found on monocytes, macrophages, eosinophils, neutrophils and dendritic cells. It binds immunoglobulin G (IgG) antibody-antigen complexes at its Fc region to trigger key immune responses. CD64 contains three immunoglobulin-fold extracellular domains (D1, D2 and D3) and a membrane-spanning region. Despite the importance of CD64, no solution structure for this is known to date. To investigate this, we used analytical ultracentrifugation, small-angle X-ray scattering, and atomistic modelling. Analytical ultracentrifugation revealed that CD64 was monomeric with a sedimentation coefficient s020,w of 2.53 S, together with some dimer. Small-angle X-ray scattering showed that its radius of gyration RG was 3.3–3.4 nm and increased at higher concentrations to indicate low dimerization. Monte Carlo modelling implemented in the SASSIE-web package generated 279,162 physically-realistic trial CD64 structures. From these, the scattering best-fit models at the lowest measured concentrations that minimised dimers revealed that the D1, D2 and D3 domains were structurally similar to those seen in three CD64 crystal structures, but showed previously unreported flexibility between D1, D2 and D3. Despite the limitations of the scattering data, the superimposition of the CD64 solution structures onto crystal structures of the IgG Fc-CD64 complex showed that the CD64 domains do not sterically clash with the IgG Fc region, i.e. the solution structure of CD64 was sufficiently compact to allow IgG to bind to its high-affinity Fcγ receptor. This improved understanding may result in novel approaches to inhibit CD64 function, and opens the way for the solution study of the full-length CD64-IgG complex.</p
The solution structure of the unbound IgG Fc receptor CD64 resembles its crystal structure: Implications for function
No full textThe solution structure of the unbound IgG Fc receptor CD64 resembles its crystal structure: Implications for function
No full textFcγRI (CD64) is the only high-affinity Fcγ receptor found on monocytes, macrophages, eosinophils, neutrophils and dendritic cells. It binds immunoglobulin G (IgG) antibody-antigen complexes at its Fc region to trigger key immune responses. CD64 contains three immunoglobulin-fold extracellular domains (D1, D2 and D3) and a membrane-spanning region. Despite the importance of CD64, no solution structure for this is known to date. To investigate this, we used analytical ultracentrifugation, small-angle X-ray scattering, and atomistic modelling. Analytical ultracentrifugation revealed that CD64 was monomeric with a sedimentation coefficient s020,w of 2.53 S, together with some dimer. Small-angle X-ray scattering showed that its radius of gyration RG was 3.3–3.4 nm and increased at higher concentrations to indicate low dimerization. Monte Carlo modelling implemented in the SASSIE-web package generated 279,162 physically-realistic trial CD64 structures. From these, the scattering best-fit models at the lowest measured concentrations that minimised dimers revealed that the D1, D2 and D3 domains were structurally similar to those seen in three CD64 crystal structures, but showed previously unreported flexibility between D1, D2 and D3. Despite the limitations of the scattering data, the superimposition of the CD64 solution structures onto crystal structures of the IgG Fc-CD64 complex showed that the CD64 domains do not sterically clash with the IgG Fc region, i.e. the solution structure of CD64 was sufficiently compact to allow IgG to bind to its high-affinity Fcγ receptor. This improved understanding may result in novel approaches to inhibit CD64 function, and opens the way for the solution study of the full-length CD64-IgG complex
A 'third culture' in economics? An essay on Smith, Confucius and the rise of China
No full textChina's rise drives a growing impact of China on economics. So far, this mainly works via the force of example, but there is also an emerging role of Chinese thinking in economics. This paper raises the question how far Chinese perspectives can affect certain foundational principles in economics, such as the assumptions on individualism and self-interest allegedly originating in Adam Smith. I embark on sketching a 'third culture' in economics, employing a notion from cross-cultural communication theory, which starts out from the observation that the Chinese model was already influential during the European enlightenment, especially on physiocracy, suggesting a particular conceptualization of the relation between good government and a liberal market economy. I relate this observation with the current revisionist view on China's economic history which has revealed the strong role of markets in the context of informal institutions, and thereby explains the strong performance of the Chinese economy in pre-industrial times. I sketch the cultural legacy of this pattern for traditional Chinese conceptions of social interaction and behavior, which are still strong in rural society until today. These different strands of argument are woven together in a comparison between Confucian thinking and Adam Smith, especially with regard to the 'Theory of Moral Sentiments', which ends up in identifying a number of conceptual family resemblances between the two. I conclude with sketching a 'third culture' in economics in which moral aspects of economic action loom large, as well as contextualized thinking in economic policies. --Confucianism,Adam Smith,physiocracy,collectivism and individualism,social relations in China,morality,economy of Imperial China
The supporting information zip file provides the 100 best-fit models for CD64 corresponding to the fit searches of the X-ray curve at 0.11 mg/ml.
No full textThe supporting information zip file provides the 100 best-fit models for CD64 corresponding to the fit searches of the X-ray curve at 0.11 mg/ml.</p
Making sense of institutional change in China: The cultural dimension of economic growth and modernization
No full textBuilding on a new model of institutions proposed by Aoki and the systemic approach to economic civilizations outlined by Kuran, this paper attempts an analysis of the cultural foundations of recent Chinese economic development. I argue that the cultural impact needs to be conceived as a creative process that involves linguistic entities and other public social items in order to provide integrative meaning to economic interactions and identities to different agents involved. I focus on three phenomena that stand at the center of economic culture in China, networks, localism and modernism. I eschew the standard dualism of individualism vs. collectivism in favour of a more detailed view on the self in social relationships. The Chinese pattern of social relations, guanxi, is also a constituent of localism, i.e. a peculiar arrangement and resulting dynamics of central-local interactions in governing the economy. Localism is balanced by culturalist controls of the center, which in contemporary China builds on the worldview of modernism. Thus, economic modernization is a cultural phenomenon on its own sake. I summarize these interactions in a process analysis based on Aoki's framework. --Aoki,culture and the economy,emics/etics,guanxi,relational collectivism,central/local government relations,culturalism,population quality,consumerism
CCP-SAS - Novel Approaches for the Atomistic Modelling of Small Angle Scattering Data in Biology
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