Hypoxia weakens mussel attachment by interrupting DOPA cross-linking during adhesive plaque curing

Marine mussels ( Mytilus spp.) attach to a wide variety of surfaces underwater using a network of byssal threads, each tipped with a protein-based adhesive plaque that uses the surrounding seawater environment as a curing agent. Plaques undergo environmental post-processing, requiring a basic seawater pH be maintained for up to 8 days for the adhesive to strengthen completely. Given the sensitivity of plaques to local pH conditions long after deposition, we investigated the effect of other aspects of the seawater environment that are known to vary in nearshore habitats on plaque curing. The effect of seawater temperature, salinity and dissolved oxygen concentration were investigated using tensile testing, atomic force microscopy and amino acid compositional analysis. High temperature (30°C) and hyposalinity (1 PSU) had no effect on adhesion strength, while incubation in hypoxia (0.9 mg l −1 ) caused plaques to have a mottled coloration and prematurely peel from substrates, leading to a 51% decrease in adhesion strength. AFM imaging of the plaque cuticle found that plaques cured in hypoxia had regions of lower stiffness throughout, indicative of reductions in DOPA cross-linking between adhesive proteins. A better understanding of the dynamics of plaque curing could aid in the design of better synthetic adhesives, particularly in medicine where adhesion must take place within wet body cavities.

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Bioinspired Synthesis of Cross-Linking of Dopamine-Containing Block Copolymers to Form Thermosensitive Covalent Hydrogels

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.531-532.238 ◽

2012 ◽

Vol 531-532 ◽

pp. 238-241 ◽

Cited By ~ 1

Author(s):

Kui Huang ◽

Jin San Chen ◽

Yang Liu

Keyword(s):

Sol Gel ◽

Coupling Efficiency ◽

Pluronic F127 ◽

Cross Linking ◽

Inversion Method ◽

Sustained Drug Delivery ◽

Vis Spectroscopy ◽

Marine Mussels ◽

Mussel Adhesive ◽

Adhesive Proteins

Marine mussels secrete remarkable mussel adhesive proteins (MAPs) for adherence to the substrates upon which they reside. Inspired by the intermolecular cross-linking characteristics of MAPs, we report the synthesis of thermosensitive dopamine modified Pluronic copolymer (PluF127-Dopa) with high coupling efficiency. Under certain temperature and concentration, PluF127-Dopa copolymers in aqueous solution self-assemble into micelles and are able to rapidly form a more stable hydrogels upon addition of oxidizing reagents such as NaIO4, resulting from oxidative cross-linking of dopamine. UV-vis spectroscopy was utilized to identify the reaction intermediates. The sol-gel transition curves of cross-linked PluF127-Dopa hydrogels (CL-PluF127-Dopa) were determined by a vial inversion method. The critical gelation concentration of CL-PluF127-Dopa hydrogels was significantly lower than those for PluF127-Dopa and unmodified Pluronic F127. The apparent mechanical strength of CL-PluF127-Dopa hydrogels was dramatically enhanced compared to those unmodified Pluronic copolymer hydrogels, suitable for sustained drug delivery. These new biomimetic materials are expected to have potential uses in biomedical applications.

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The role of cross-linking in the scratch resistance of organic coatings: An investigation using Atomic Force Microscopy

Wear ◽

10.1016/j.wear.2018.11.027 ◽

2019 ◽

Vol 418-419 ◽

pp. 151-159 ◽

Cited By ~ 4

Author(s):

Juan F. Gonzalez-Martinez ◽

Erum Kakar ◽

Stefan Erkselius ◽

Nicola Rehnberg ◽

Javier Sotres

Keyword(s):

Atomic Force Microscopy ◽

Scratch Resistance ◽

Organic Coatings ◽

Cross Linking ◽

Force Microscopy ◽

Atomic Force

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Characterization of nit sheath protein functions and transglutaminase-mediated cross-linking in the human head louse, Pediculus humanus capitis

Parasites & Vectors ◽

10.1186/s13071-021-04914-z ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Ju Hyeon Kim ◽

Do Eun Lee ◽

SangYoun Park ◽

John M. Clark ◽

Si Hyeock Lee

Keyword(s):

Rna Interference ◽

Head Louse ◽

Structural Proteins ◽

Cross Linking ◽

Functional Importance ◽

Homologous Proteins ◽

Egg Hatching ◽

Additional Function ◽

Accessory Glands ◽

Adhesive Proteins

Abstract Background Head louse females secrete liquid glue during oviposition, which is solidified to form the nit sheath over the egg. Recently, two homologous proteins, named louse nit sheath protein (LNSP) 1 and LNSP 2, were identified as adhesive proteins but the precise mechanism of nit sheath solidification is unknown. Methods We determined the temporal transcriptome profiles of the head louse accessory glands plus oviduct, from which putative major structural proteins and those with functional importance were deduced. A series of RNA interference (RNAi) experiments and treatment of an inhibitor were conducted to elucidate the function and action mechanism of each component. Results By transcriptome profiling of genes expressed in the louse accessory glands plus uterus, the LNSP1 and LNSP2 along with two hypothetical proteins were confirmed to be the major structural proteins. In addition, several proteins with functional importance, including transglutaminase (TG), defensin 1 and defensin 2, were identified. When LNSP1 was knocked down via RNA interference, most eggs became nonviable via desiccation, suggesting its role in desiccation resistance. Knockdown of LNSP2, however, resulted in oviposition failure, which suggests that LNSP2 may serve as the basic platform to form the nit sheath and may have an additional function of lubrication. Knockdown of TG also impaired egg hatching, demonstrating its role in the cross-linking of nit sheath proteins. The role of TG in cross-linking was further confirmed by injecting or hair coating of GGsTop, a TG inhibitor. Conclusions Both LNSP1 and LNSP2 are essential for maintaining egg viability besides their function as glue. The TG-mediated cross-linking plays critical roles in water preservation that are essential for ensuring normal embryogenesis. TG-mediated cross-linking mechanism can be employed as a therapeutic target to control human louse eggs, and any topically applied TG inhibitors can be exploited as potential ovicidal agents. Graphical abstract

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Spin-Coated Polysaccharide-Based Multilayered Freestanding Films with Adhesive and Bioactive Moieties

Molecules ◽

10.3390/molecules25040840 ◽

2020 ◽

Vol 25 (4) ◽

pp. 840 ◽

Cited By ~ 3

Author(s):

Joana Moreira ◽

Ana C. Vale ◽

Ricardo A. Pires ◽

Gabriela Botelho ◽

Rui L. Reis ◽

...

Keyword(s):

Weight Loss ◽

Coating Layer ◽

Synergetic Effect ◽

Layer By Layer ◽

Negative Effects ◽

Biological Assays ◽

Modified Polymers ◽

Marine Mussels ◽

Cellular Metabolic Activity ◽

Adhesive Proteins

Freestanding films based on catechol functionalized chitosan (CHI), hyaluronic acid (HA), and bioglass nanoparticles (BGNPs) were developed by spin-coating layer-by-layer assembly (SA-LbL). The catechol groups of 3,4-dihydroxy-l-phenylalanine (DOPA) present in the marine mussels adhesive proteins (MAPs) are the main factors responsible for their characteristic strong wet adhesion. Then, the produced films were cross-linked with genipin to improve their stability in wet state. Overall, the incorporation of BGNPs resulted in thicker and bioactive films, hydrophilic and rougher surfaces, reduced swelling, higher weight loss, and lower stiffness. The incorporation of catechol groups onto the films showed a significant increase in the films’ adhesion and stiffness, lower swelling, and weight loss. Interestingly, a synergetic effect on the stiffness increase was observed upon the combined incorporation of BGNPs with catechol-modified polymers, given that such films were the stiffest. Regarding the biological assays, the films exhibited no negative effects on cellular viability, adhesion, and proliferation, and the BGNPs seemed to promote higher cellular metabolic activity. These bioactive LbL freestanding films combine enhanced adhesion with improved mechanical properties and could find applications in the biomedical field, such as guided hard tissue regeneration membranes.

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Measurement Method of Adhesion Strength between Inorganic Materials and Polymer by Using Atomic Force Microscopy

Journal of the Ceramic Society of Japan ◽

10.2109/jcersj.102.1102 ◽

1994 ◽

Vol 102 (1192) ◽

pp. 1102-1104 ◽

Cited By ~ 2

Author(s):

Akira KAWAI ◽

Hitoshi NAGATA ◽

Masasuke TAKATA

Keyword(s):

Atomic Force Microscopy ◽

Adhesion Strength ◽

Measurement Method ◽

Inorganic Materials ◽

Force Microscopy ◽

Atomic Force

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Progressive seawater acidification on the Great Barrier Reef continental shelf

Scientific Reports ◽

10.1038/s41598-020-75293-1 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Katharina E. Fabricius ◽

Craig Neill ◽

Erik Van Ooijen ◽

Joy N. Smith ◽

Bronte Tilbrook

Keyword(s):

Coral Reefs ◽

Continental Shelf ◽

Great Barrier Reef ◽

Ocean Acidification ◽

Seawater Temperature ◽

Barrier Reef ◽

Saturation State ◽

Seawater Acidification ◽

Seawater Ph ◽

Seawater Samples

Abstract Coral reefs are highly sensitive to ocean acidification due to rising atmospheric CO2 concentrations. We present 10 years of data (2009–2019) on the long-term trends and sources of variation in the carbon chemistry from two fixed stations in the Australian Great Barrier Reef. Data from the subtropical mid-shelf GBRWIS comprised 3-h instrument records, and those from the tropical coastal NRSYON were monthly seawater samples. Both stations recorded significant variation in seawater CO2 fugacity (fCO2), attributable to seasonal, daytime, temperature and salinity fluctuations. Superimposed over this variation, fCO2 progressively increased by > 2.0 ± 0.3 µatm year−1 at both stations. Seawater temperature and salinity also increased throughout the decade, whereas seawater pH and the saturation state of aragonite declined. The decadal upward fCO2 trend remained significant in temperature- and salinity-normalised data. Indeed, annual fCO2 minima are now higher than estimated fCO2 maxima in the early 1960s, with mean fCO2 now ~ 28% higher than 60 years ago. Our data indicate that carbonate dissolution from the seafloor is currently unable to buffer the Great Barrier Reef against ocean acidification. This is of great concern for the thousands of coral reefs and other diverse marine ecosystems located in this vast continental shelf system.

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Influence of Surface Pretreatment on Carbon Coating of Cutting Tools Using PVD

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.236-237.530 ◽

2012 ◽

Vol 236-237 ◽

pp. 530-535

Author(s):

D.N. Awang Shri ◽

J. Ramli ◽

N.A. Alang ◽

M.M. Mahat

Keyword(s):

Adhesion Strength ◽

Physical Vapor Deposition ◽

Carbon Coating ◽

Cutting Tool ◽

Cutting Tools ◽

Rake Angle ◽

Acid Etching ◽

Surface Pretreatment ◽

Force Microscopy ◽

Atomic Force

Alumina (Al2O3) cutting tools have been coated with carbon coating using physical vapor deposition (PVD) to improve its wear resistance. The cutting tools were subjected to surface pretreatments namely blasting and acid etching to improve the coating adhesion onto the substrates. The effects of pretreatments on the cutting tools topography prior to deposition were investigated using atomic force microscopy (AFM) while the surface morphology was investigated using scanning electron microscopy (SEM). The rake angle of the coated cutting tool and surface roughness of the cutting edge were investigated using infinite focus microscope. The adhesion strength of the carbon coating was investigated using microscratch. This study shows that although the coating were deposited evenly on all samples, the cutting tool that was blasted prior to deposition has better adhesion strength when compared to acid etching and no-pretreatment.

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