Confocal Raman Micro-Spectroscopy Analysis of Mussel Foot
LIANG Zheng-wei1, 3, 4, DU Zeng-feng1, 4, LI Chao-lun1, 3, 4, WANG Min-xiao1, 3, 4, WANG Bing1, 4, ZHANG Xin1, 2, 3, 4*, YAN Jun1
1. CAS Key Laboratory of Marine Geology and Environment & Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
2. Laboratory for Marine Geology, Pilot National Laboratory for Marine Science and Technology，Qingdao 266061, China
3. University of Chinese Academy of Sciences, Beijing 100049, China
4. Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China
Abstract：Mussels are widely distributed in various marine environments, from shallow seas to cold seeps and hydrothermal vents in the deep oceans, because of its excellent adaptabilityin different physicochemical conditions. Mussels anchor themselves on the tough substrate exposed on the seabed, such authigenic carbonate crusts or rock outcrops with adhesive protein secreted by mussel foot. This protein is a natural renewable biological adhesive available in various marine environments and mussel byssus presents such as high adhesive, high toughness and resistance to water. The adhesive protein has great potential and application prospect in biotechnology and medicine field, and it has become a research hotspot nowadays. Raman spectroscopy is a kind of non-destructive and non-invasive detection technique which can provide molecular biochemical information of organisms. In this paper, SEM and confocal Raman micro-spectroscopy are used to investigatethe apparent difference of mussel foot byssus, the secreted protein composition and distribution characteristics of mussel foot gland. Based on the apparent morphological differences of deep-sea mussels and sallow-sea mussels by SEM, two kind of mussels foot tissues are detected with confocal Raman micro-spectroscopy and acquire Raman spectra and 2D Raman color-coded image of three glands. The components and relative distribution of three glands of two mussels are compared and byssus differences caused by the glands distribution are analyzed. Meanwhile, considering the living environments of the two kind of mussels, we think that the mussel byssus appearance difference and foot glands distribution is a kind of adaptation mechanism to the environment. The Raman spectra suggest the components of two mussels foot glands: the higher intensity at 1 242 and 1 269 cm-1to the other two peaks (1 318 and 1 337 cm-1) of the amide Ⅲ signals indicates that the core gland is a higher degree of conformational order protein. The proteins that comprise theplaque and cuticle enrich amino acid tyrosine (Tyr) at 643，830，850 and 1 615 cm-1 and post-translationally converted to 3,4-dihydroxyphenylalanine (DOPA) at 785 cm-1; shallow-sea mussels present high intensity collagen protein at 1 043 cm-1. Raman imaging shows the glands distribution feature: deep-sea mussels foot glands distribution concentration and shallow-sea mussels foot glands distribution dispersion, which suggests that the glands distribution may be a kind of mechanism for the mussels to adapt different environments. The results indicate that confocal Raman micro-spectroscopy can be used in the analysis of the mussel foot glands distribution characteristics in different environments, and has great prospect to be applied in the micro-analysis of the biological samples.
Key words：Confocal Raman spectroscopy; Mussel foot gland; Adhesive protein
[1] North M A, Del Grosso C A, Wilker J J. ACS Applied Materials & Interfaces, 2017, 9(8): 7866.
[2] Filippidi E, Demartini D G, Paula M D M, et al. Journal of the Royal Society Interface, 2015, 12(113): 20150827.
[3] Li S, Zhan A, Gao Y, et al. Frontiers in Physiology, 2018, 9: 418.
[4] Inoue K, Takeuchi Y, Miki D, et al. FEBS Journal, 1996, 239(1): 172.
[5] Schmitt C N Z, Winter A, Bertinetti L, et al. Journal of the Royal Society Interface, 2015, 12(110): 20150466.
[6] Priemel T, Degtyar E, Dean M N, et al. Nature Communications, 2017, 8: 14539.
[7] Ooka A A, Garrell R L. Biopolymers, 2000, 57(2): 92.
[8] Movasaghi Z, Rehman S, Rehman I U. Applied Spectroscopy Reviews, 2007, 42(5): 495.
[9] Kallepitis C, Bergholt M S, Mazo M M, et al. Nature Communications, 2017, 8: 14843.
