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Microscopy Experiments
Published in Raimund J. Ober, E. Sally Ward, Jerry Chao, Quantitative Bioimaging, 2020
Raimund J. Ober, E. Sally Ward, Jerry Chao
This leads us to revisit the association experiment discussed in Section 11.1.2, involving FcRn and lysosomes. The experiment described there used GFP as a label for FcRn. Therefore, considering the significantly reduced GFP emission at lysosomal pH, it is important to examine the experiment in more detail. The labeling of FcRn with GFP was done by attaching GFP to the C-terminus of FcRn. Since FcRn is a type I transmembrane protein (Fig. 9.3), this means that the expression of FcRn-GFP on membranes is such that GFP is exposed to the cytosol. The result of the experiment thus indicates that there is no significant presence of FcRn on the lysosomal membrane. However, based on this experiment we cannot say much in terms of the presence of FcRn in the lumen of lysosomes. The absence of GFP signal from the lysosomal lumen could be due to FcRn not being there, or it could be due to the GFP signal being undetectable because of the low lysosomal pH. In fact, in experiments using the pH-insensitive mRFP1 as a label for FcRn, it has been shown that FcRn can be detected in the lumen of lysosomes. However, since lysosomes are the compartments responsible for breaking down proteins and other macromolecules, it is not completely surprising to find evidence of any protein in lysosomes.
Label-free sensitive detection of MUC1 using a liquid crystal based-system
Published in Liquid Crystals, 2020
Thai Duong Song Duong, Chang-Hyun Jang
MUC1 is a type I transmembrane protein primarily made up of 20-amino acid tandem repeats, and a cytoplasmic tail of 69 amino acids [1]. MUC1 is expressed on the surface of the oesophageal and ductal epithelial cells of the pancreas and the fundic gland cells of the stomach. It has also been detected in the cells of adenocarcinomas, including breast [2], lung [3], prostate [4], gastric [5], colorectal [6], ovarian [7], pancreatic [5] and bladder carcinomas [8]. Moreover, the expression of MUC1 in these tissues lacks its endogenous regulation, resulting in ubiquitous, random expression of this protein all over the cell surface [9]. In some cases, the expression of MUC1 is increased to a level where it can even be detected at high concentrations in the blood [10]. Cancer antigen 15–3 concentration (soluble MUC1) [11] above the clinical threshold (30 U/ml) was detected in about 10% of women with early localised breast cancer and about 70% of those with metastatic breast cancer [12,13]. For these reasons, MUC1 is an attractive potential serum biomarker for the early detection of tumours in cancer diagnostics.