Engineering pH-responsive switching of donor–π–acceptor chromophore alignments along a peptide nanotube scaffold

Previous studies from our laboratory have confirmed that cultures of LLC-PK1 cells exhibit pH-responsive alterations in ammonia metabolism produced by changes in media bicarbonate concentration. To further elucidate the mechanism of ammonia regulation, studies were carried out using parallel cultures of still and rocked LLC-PK1 cells subjected to acute alterations in media pH by either metabolic or respiratory acid-base manipulations. When media pH was altered by modifying PCO2 levels, the response of ammonia and alanine production by rocked culture was identical to the changes observed with metabolic acid-base maneuvers. Furthermore, both metabolic and respiratory acute acidosis resulted in a fall of intracellular alpha-ketoglutarate concentrations in these cells. In contrast, standard still cultures subjected to acute acidosis/alkalosis by metabolic and respiratory manipulations did not exert any significant change in ammonia and alanine production or in intracellular alpha-ketoglutarate concentration. Measurements of intracellular pH (pHi) by the 5,5-[2-14C]dimethyloxazolidine-2,4-dione method in rocked cells demonstrated changes in pHi parallel to media pH changes induced by both metabolic and respiratory acid-base maneuvers. Despite the absence of pH-responsive ammonia-genesis in still cultured cells the pHi values were altered in a fashion similar to their rocked counterparts, indicating the lack of an effect of the pHi signal on ammonia metabolism.

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pH-Responsive Properties of Asymmetric Nanopapers of Nanofibrillated Cellulose

Nanomaterials ◽

10.3390/nano10071380 ◽

2020 ◽

Vol 10 (7) ◽

pp. 1380

Author(s):

Maud Chemin ◽

Baptiste Beaumal ◽

Bernard Cathala ◽

Ana Villares

Keyword(s):

Carboxylic Acid ◽

Reaction Times ◽

Nanofibrillated Cellulose ◽

Ph Responsive ◽

Tempo Oxidation ◽

Ph Changes ◽

Charge Concentration ◽

Amine Groups ◽

Layer Composition ◽

Electrostatic Repulsions

Inspired by plant movements driven by the arrangement of cellulose, we have fabricated nanopapers of nanofibrillated cellulose (NFC) showing actuation under pH changes. Bending was achieved by a concentration gradient of charged groups along the film thickness. Hence, the resulting nanopapers contained higher concentration of charged groups on one side of the film than on the opposite side, so that pH changes resulted in charge-dependent asymmetric deprotonation of the two layers. Electrostatic repulsions separate the nanofibers in the nanopaper, thus facilitating an asymmetric swelling and the subsequent expanding that results in bending. Nanofibrillated cellulose was modified by 2,2,6,6-tetramethylpiperidin-1-yloxyl radical (TEMPO) oxidation at two reaction times to get different surface concentrations of carboxylic acid groups. TEMPO-oxidized NFC was further chemically transformed into amine-modified NFC by amidation. The formation of graded nanopapers was accomplished by successive filtration of NFC dispersions with varying charge nature and/or concentration. The extent of bending was controlled by the charge concentration and the nanopaper thickness. The direction of bending was tuned by the layer composition (carboxylic acid or amine groups). In all cases, a steady-state was achieved within less than 25 s. This work opens new routes for the use of cellulosic materials as actuators.

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Engineering molecular self-assembly of perylene diimide through pH-responsive chiroptical switching

Molecular Systems Design & Engineering ◽

10.1039/c6me00012f ◽

2016 ◽

Vol 1 (2) ◽

pp. 202-207 ◽

Cited By ~ 11

Author(s):

M. Pandeeswar ◽

T. Govindaraju

Keyword(s):

Self Assembly ◽

Perylene Diimide ◽

Ph Responsive ◽

1D Nanostructures ◽

Left Handed ◽

Non Covalent Interactions ◽

Covalent Interactions

The perturbation of non-covalent interactions induced by pH-responsive protonation–deprotonation in HPH resulted in reversible supramolecular chiroptical switching (left-handed to right-handed helical self-assembly) and tunable 1D nanostructures.

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MODELLING ION, WATER AND ION–WATER CLUSTER ENTERING PEPTIDE NANOTUBES

The ANZIAM Journal ◽

10.1017/s1446181115000164 ◽

2015 ◽

Vol 57 (1) ◽

pp. 62-78

Author(s):

N. THAMWATTANA

Keyword(s):

Self Assembly ◽

Water Cluster ◽

Cyclic Peptides ◽

Simple Structure ◽

Cyclic Peptide ◽

Initial Energy ◽

Jones Potential ◽

Peptide Nanotubes ◽

Organic Nanostructures ◽

Peptide Nanotube

Recently, organic nanostructures have attracted much attention, and amongst them peptide nanotubes are of interest in many fields of application including medicine and nanobiotechnology. Peptide nanotubes are formed by self-assembly of cyclic peptides with alternating L- and D-amino acids. Due to their biodegradability, flexible design and easy synthesis, many applications have been proposed such as artificial transmembrane ion channels, templates for nanoparticles, mimicking pore structures, nanoscale testing tubes, biosensors and carriers for targeted drug delivery. The mechanisms of an ion, a water molecule and an ion–water cluster entering into a peptide nanotube of structure cyclo[(-D-Ala-L-Ala-)$_{4}$] are explored here. In particular, the Lennard-Jones potential and a continuum approach are employed to determine three entering mechanisms: (i) through the tube open end, (ii) through a region between each cyclic peptide ring and (iii) around the edge of the tube open end. The results show that while entering the nanotube by method (i) is possible, an ion or a molecule requires initial energy to overcome an energetic barrier to be able to enter the nanotube through positions (ii) and (iii). Due to its simple structure, the D-, L-Ala cyclopeptide nanotube is chosen in this model; however, it can be easily extended to include more complicated nanotubes.

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Self-Assembly Effects of Cyclic Peptide Dimers: Molecular Modeling Study

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.353-358.2257 ◽

2007 ◽

Vol 353-358 ◽

pp. 2257-2260

Author(s):

Jing Chuan Zhu ◽

Jie Cheng ◽

Bo Liu

Keyword(s):

Self Assembly ◽

Cyclic Peptides ◽

Cyclic Peptide ◽

The Self ◽

Transport Channel ◽

Structure And Property ◽

Self Assembling ◽

Intermolecular Hydrogen Bonding Interaction ◽

Bonding Interaction ◽

Peptide Nanotube

The cyclic peptides can self-assemble into β-sheet like antiparallel tubular ensembles through intermolecular hydrogen-bonding interaction. Under the self-assembling effects of the dimer subunits, various aggregate properties may alter with the change of the structure. The relationship between the property and structure of ensembles is extremely important for designing new nanostructures. Molecular mechanics (MM) and molecular dynamics (MD) were employed to investigate the structure and property of single dimer and dimer-ensemble from cyclo-[D-Phe-(1R, 3S)-γ-Acc]3. Results reveal that the single dimer cannot adsorb CHCl3 molecule into its cavity, while the two-dimer ensemble can do. It suggests that the self-assembled cyclic peptide nanotube from the dimer-ensemble may act as the transport channel of CHCl3 molecules.

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pH-RESPONSIVE PERMEATION OF BILAYER-COATED CAPSULE MEMBRANES BY AMBIENT pH CHANGES

Chemistry Letters ◽

10.1246/cl.1984.1251 ◽

1984 ◽

Vol 13 (7) ◽

pp. 1251-1254 ◽

Cited By ~ 9

Author(s):

Yoshio Okahata ◽

Takahiro Seki

Keyword(s):

Ph Responsive ◽

Ph Changes

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Live cell imaging of lysosomal pH changes with pH responsive ratiometric lanthanide probes

Chemical Communications ◽

10.1039/c2cc34267g ◽

2012 ◽

Vol 48 (68) ◽

pp. 8520 ◽

Cited By ~ 113

Author(s):

David G. Smith ◽

Brian K. McMahon ◽

Robert Pal ◽

David Parker

Keyword(s):

Live Cell Imaging ◽

Cell Imaging ◽

Live Cell ◽

Ph Responsive ◽

Lysosomal Ph ◽

Ph Changes

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Single molecule optical diffraction: A tool for understanding the structure of triple stranded left-hand helical cellulose

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100157103 ◽

1989 ◽

Vol 47 ◽

pp. 1024-1025

Author(s):

George C. Ruben ◽

William Krakow

Keyword(s):

Single Molecule ◽

Helical Structure ◽

Optical Diffraction ◽

Maximum Diameter ◽

Primary Cell Wall ◽

Cellulose Synthesis ◽

Left Hand ◽

Left Handed ◽

Freeze Dried ◽

Diffraction Patterns

Tobacco primary cell wall and normal bacterial Acetobacter xylinum cellulose formation produced a 36.8±3Å triple-stranded left-hand helical microfibril in freeze-dried Pt-C replicas and in negatively stained preparations for TEM. As three submicrofibril strands exit the wall of Axylinum , they twist together to form a left-hand helical microfibril. This process is driven by the left-hand helical structure of the submicrofibril and by cellulose synthesis. That is, as the submicrofibril is elongating at the wall, it is also being left-hand twisted and twisted together with two other submicrofibrils. The submicrofibril appears to have the dimensions of a nine (l-4)-ß-D-glucan parallel chain crystalline unit whose long, 23Å, and short, 19Å, diagonals form major and minor left-handed axial surface ridges every 36Å.The computer generated optical diffraction of this model and its corresponding image have been compared. The submicrofibril model was used to construct a microfibril model. This model and corresponding microfibril images have also been optically diffracted and comparedIn this paper we compare two less complex microfibril models. The first model (Fig. 1a) is constructed with cylindrical submicrofibrils. The second model (Fig. 2a) is also constructed with three submicrofibrils but with a single 23 Å diagonal, projecting from a rounded cross section and left-hand helically twisted, with a 36Å repeat, similar to the original model (45°±10° crossover angle). The submicrofibrils cross the microfibril axis at roughly a 45°±10° angle, the same crossover angle observed in microflbril TEM images. These models were constructed so that the maximum diameter of the submicrofibrils was 23Å and the overall microfibril diameters were similar to Pt-C coated image diameters of ∼50Å and not the actual diameter of 36.5Å. The methods for computing optical diffraction patterns have been published before.

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