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The Human Immune System Seen from a Biomedical Engineering Viewpoint
Published in Robert B. Northrop, Endogenous and Exogenous Regulation and Control of Physiological Systems, 2020
The antibodies produced by activated plasma B-cells have a unique molecular structure: They are “Y” shaped, with the Ag-binding domain (paratope) lying between the arms of the Y. Molecular diversity in encoding the binding domain structure gives the possibility of about 106 different Ab paratopes in the human at a given time. The stem of the Y is made from the paired ends of two “heavy protein chains” of over 400 amino acids (AAs) in length. The arms of the Y are also paired, the ends of the heavy chains each with a light chain of over 200 AA. (See Figure 10.3 for an antibody schematic.) As mentioned above, there are five classes of circulating antibodies: IgA, IgD, IgE, IgG, and IgM. The heavy chains that make up these Abs are called alpha, delta, epsilon, gamma, and mu, respectively. The light chains are called kappa or lambda. Genetically randomized, variable regions of the light and heavy chains form the paratope sites, one in each arm of the “Y”. Some Abs, however, are formed from a fusion of as many as 10 light and 10 heavy chains and hence have 10 binding sites.156 The protein structure of the stem region of the Y is relatively constant and contains a constant Fc binding site through which NK cells, macrophages, mast cells, etc. can recognize and bind to Abs. If the Ab has bound to a cell-surface Ag, NK cells can bind to the Fc site and then secrete perforin which kills the cell. Macrophages clean the mess up.
Enzyme Kinetics and Drugs as Enzyme Inhibitors
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Plasma cells normally produce large amounts of antibodies (immunoglobulins) in response to the immune system. In case of malignant transformation this property gets lost and is substituted by the production of a single type of abnormal monoclonal or M protein (monoclonal gammopathy) not being able to fight infections. Myeloma cells may also produce too many light chains that accumulate in tissues to amyloids (light chain amyloidosis). For example, their agglomeration in the heart may cause congestive heart failure, or harm the kidney. Furthermore the exceeding growth of plasma cells in the bone marrow proceeds at the expense of normal blood-forming cells with the consequence of anemia; thrombocytopenia (a low platelet count in the blood) may lead to development of external bleeding; a decrease in the number leukocytes (leukopenia) is tantamount to an increased risk of infections.
Cellular and Molecular Basis of Human Biology
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
These mobile proteins are the products of committed B-cells, plasma cells. In human, 5 classes of antibodies are produced: IgM, IgG, IgA, IgE, and IgD. These classes of antibodies are immunologically distinguished by the difference of their heavy chain sequences. As for light chain, only two classes are produced, lambda and kappa chains. In human, IgG has 4 subclasses, IgG1, IgG2, IgG3, and IgG4; whereas IgA has 2 subclasses, IgA1 and IgA2. IgD is a B cell surface receptor and is not usually released into the extracellular environment. Whereas IgM is the initially released antibody response, IgG comes later in the immune response but become the dominant class, constituting 80% of circulating antibodies. IgA is primarily responsible for mucosal immune defense. IgE involves in allergic reaction by binding on IgE receptors of mast cells, triggering mast cells to release histamines.
Bioprocessing of recombinant proteins from Escherichia coli inclusion bodies: insights from structure-function relationship for novel applications
Published in Preparative Biochemistry & Biotechnology, 2023
Kajal Kachhawaha, Santanu Singh, Khyati Joshi, Priyanka Nain, Sumit K. Singh
Peptide mapping is a useful method for the identification of product-related impurities formed during protein refolding. The biggest advantage of peptide mapping is when used with mass spectrometry to confidently identify site-specific modifications on the proteins.[168] In a recent application of peptide mapping for studying protein refolding, the dynamics of covalent and non-covalent interactions during the refolding of the light chain, heavy chain, and antibody fragment were studied. It was found that covalent interaction (disulfide bond formation) was the major driving force for protein refolding.[169] Further, multi-attribute monitoring (MAM) workflows are currently widely used for the discovery of unknown intermediates formed during the protein refolding. This allows for better optimization of the protein refolding process to enhance yields.[170]
Processing trends of silk fibers: Silk degumming, regeneration and physical functionalization
Published in The Journal of The Textile Institute, 2020
Shivani Rastogi, Balasubramanian Kandasubramanian
The heavy chain of fibroins comprises of highly repetitive hydrophobic amino acid residues. 432 copies of GAGAGS and 120 copies of GAGAGY. However, the light chain with the molecular weight 25,800 Da, comprises of hydrophilic non-repetitive sequences of 244 amino acid residues (Qi et al., 2017). The heavy and light chain of silk fibroins is connected via disulfide bond formed between Cys-20 of the heavy chain and Cys-172 of the light chain. The glycoprotein P25 (30 KDa) attaches to heavy-light chain complex by hydrophobic interactions and functions by maintaining the structural integrity. Silk fibroins exhibit both crystalline (∼55%) and amorphous (∼45%) nature. The crystalline regions give strength and stiffness to the fiber, and amorphous regions give elasticity (Porter & Vollrath, 2009; Giesa, Arslan, Pugno, & Buehler, 2011; Keten, Xu, Ihle, & Buehler, 2010; Thiel, Guess, & Viney, 1997). The different secondary structures formed by distinct amino acid sequences exhibit both amorphous and crystalline nature, as shown in Table 2.
Influence of microcystins-LR (MC-LR) on autophagy in human neuroblastoma SK-N-SH cells
Published in Journal of Toxicology and Environmental Health, Part A, 2019
Yue Yang, Cong Wen, Shuilin Zheng, Wenya Liu, Jihua Chen, Xiangling Feng, Xiaoyan Wang, Fei Yang, Zhen Ding
Based upon preliminary experiments the IC50 for MC-LR was 30 μmol/L after 48 hr (Figure 1). Subsequently, cell experiments were conducted with 15 μmol/L (1/2 IC50) and 30 μmol/L MC-LR levels. To investigate protein expression and subcellular localization, indirect immunofluorescence assay was performed (Kanlaya et al. 2019). The SK-N-SH cells were seeded in 24 well plates on a coverslip at a density 2 × 104 cells/well, cultured for 24 hr and medium discarded. Subsequently, cells were exposed to MC-LR (30 μmol/L, the IC50 value) for 48 hr. It should be noted that experiments were also conducted with 15 μmol/L and the findings were similar (data not shown). The cells were washed with PBS and fixed with 4% paraformaldehyde solution for 30 min, permeabilized with 0.25% Triton-X for 30 min, and blocked with 3% BSA for 30 min. After washing, cells were incubated with light chain 3 (LC3) antibody for 2 hr at room temperature. After washing, cells were incubated with coralite488–conjugated goat anti-rabbit IgG for 1 hr at room temperature. Nuclei were counterstained by 4ʹ, 6-diamidino-2-phenylindole (DAPI) for 5 min. Finally, cells were washed with PBS and coverslips mounted using anti-fade fluorescence mounting medium (Solarbio Science & Technology Co., Ltd. (Beijing, China)) on slides and photographed using fluorescence microscope (Nikon, Japan).