8 research outputs found
A Mini-Review on Reflectins, from Biochemical Properties to Bio-Inspired Applications
Some cephalopods (squids, octopuses, and cuttlefishes) produce dynamic structural colors, for camouflage or communication. The key to this remarkable capability is one group of specialized cells called iridocytes, which contain aligned membrane-enclosed platelets of high-reflective reflectins and work as intracellular Bragg reflectors. These reflectins have unusual amino acid compositions and sequential properties, which endows them with functional characteristics: an extremely high reflective index among natural proteins and the ability to answer various environmental stimuli. Based on their unique material composition and responsive self-organization properties, the material community has developed an impressive array of reflectin- or iridocyte-inspired optical systems with distinct tunable reflectance according to a series of internal and external factors. More recently, scientists have made creative attempts to engineer mammalian cells to explore the function potentials of reflectin proteins as well as their working mechanism in the cellular environment. Progress in wide scientific areas (biophysics, genomics, gene editing, etc.) brings in new opportunities to better understand reflectins and new approaches to fully utilize them. The work introduced the composition features, biochemical properties, the latest developments, future considerations of reflectins, and their inspiration applications to give newcomers a comprehensive understanding and mutually exchanged knowledge from different communities (e.g., biology and material)
Measurement of Intracellular pH Changes Based on DNA-Templated Capsid Protein Nanotubes
Intracellular pH (pHi) is a fundamental
modulator of cell function.
Minute changes in pHi may cause great effects in many cellular activities
such as metabolism and signal transduction. Herein we report an electrochemical
pHi sensor based on viral-coat proteins–DNA nanotubes modified
gold electrode. The sensor is pH-sensitive as a result of the pH-dependent
electrochemical property of methylene blue (MB) and cell permeable
owing to the polyarginine domain of the cowpea chlorotic mottle virus
(CCMV) coat protein. Moreover, because the pH sensor can be translocated
into cells without any further operations, the measurement of pHi
changes can be greatly simplified. The pH sensor has a broad pH spectrum
in the pH range from 4.0 to 9.0 and responds rapidly to the pH changes
of cells, so it may hold great potential to be a valuable tool to
study pH-dependent biological and pathological processes in the future
Self-Assembled Nanofibers for Strong Underwater Adhesion: The Trick of Barnacles
Developing
adhesives that can function underwater remains a major
challenge for bioengineering, yet many marine creatures, exemplified
as mussels and barnacles, have evolved their unique proteinaceous
adhesives for strong wet adhesion. The mechanisms underlying the strong
adhesion of these natural adhesive proteins provide rich information
for biomimetic efforts. Here, combining atomic force microscopy (AFM)
imaging and force spectroscopy, we examine the effects of pH on the
self-assembly and adhesive properties of cp19k, a key barnacle underwater
adhesive protein. For the first time, we confirm that the bacterial
recombinant <i>Balanus albicostatus</i> cp19k (rBalcp19k),
which contains no 3,4-dihydroxyphenylalanine (DOPA) or any other amino
acids with post-translational modifications, can self-assemble into
aggregated nanofibers at acidic pHs. Under moderately acidic conditions,
the adhesion strength of unassembled monomeric rBalcp19k on mica is
only slightly lower than that of a commercially available mussel adhesive
protein mixture, yet the adhesion ability of rBalcp19k monomers decreases
significantly at increased pH. In contrast, upon preassembly at acidic
and low-salinity conditions, rBalcp19k nanofibers keep stable in basic
and high-salinity seawater and display much stronger adhesion and
thus show resistance to its adverse impacts. Besides, we find that
the adhesion ability of Balcp19k is not impaired when it is combined
with an N-terminal Thioredoxin (Trx) tag, yet whether the self-assembly
property will be disrupted is not determined. Collectively, the self-assembly-enhanced
adhesion presents a previously unexplored mechanism for the strong
wet adhesion of barnacle cement proteins and may lead to the design
of barnacle-inspired adhesive materials