Tunable pH Research Articles

Photoinduced pH drops in water

A 2-hydroxyazobenzene platform has been evaluated to photorelease protons in aqueous solutions. Three different systems relying on molecular, supramolecular and polymeric strategies have been investigated in order to tune the water solubility and the thermodynamic and kinetic properties. This paper first reports on the syntheses and the physico chemical analyses for each system. Subsequently, we show that the three strategies are appropriate to reversibly photo-generate tunable pH drops in water up to one pH unit amplitude and at the 10-100 s timescale, upon transient illumination at 365 nm.

Transferrin–Terbium Complexes as Luminescent pH Sensing Devices

Three kinds of protein-metal complexes were developed as pH sensing devices in the aqueous solutions. Biological transferrin and lactoferrin proteins formed stable Tb3+ complexes, which exhibited long-lived and green luminescence signals. They showed pH-dependent luminescence changes around neutral pH, coupled with their Tb3+ complexation/decomplexation. Since fluorescein-labeled transferrin-Fe3+ complex exhibited fluorescence changes at lower pH, these three protein complexes covered wide pH-responsive ranges. The immobilized biotinylated transferrin-Tb3+ complexes on the micrometer-scaled bead also operated as a pH-responsive luminescent indicator. Since the transferrin ligand had rapid Tb3+ complexation/decomplexation process, its Tb3+ complex exhibited pH-responsive luminescence signals even in the presence of Fe3+ cation. A new series of tunable luminescent pH sensing devices were developed by combination of biological protein and luminescent lanthanide center.

PVA‐based tunable buffering membranes for isoelectric trapping separations

PVA-based buffering membranes with tunable pH values were prepared on a PVA substrate by reacting PVA, glycerol-1,3-diglycidyl ether, -NH2 group-containing buffers and -NH2 group-containing titrants in the presence of sodium hydroxide. The pH of the buffering membranes could be tuned in the 3<pH<10 range according to the Hendersson-Hasselbach equation while maintaining buffering capacities in excess of 100 mM. Detailed recipes for the preparation of six families of buffering membranes are tabulated and provided as Supporting Information. The buffering membranes were used to trap and desalt ampholyte solutions and separate proteins having a DeltapI as small as 0.1. The membranes were mechanically and hydrolytically stable and could be stored, even in 10<pH sodium hydroxide solutions, in excess of 6 months.

Tunable pH- and Temperature-Sensitive Copolymer Libraries by Reversible Addition−Fragmentation Chain Transfer Copolymerizations of Methacrylates

Reversible addition−fragmentation chain transfer (RAFT) polymerizations have been performed on a Chemspeed Accelerator SLT100 automated synthesizer to polymerize N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) at 70 °C. Azobis(isobutyronitrile) (AIBN) was used as source of radicals and 2-cyano-2-butyl dithiobenzoate (CBDB) as RAFT agent. A complete screening in composition of P(DMAEMA-stat-PEGMA) copolymers was elaborated from 0% of PEGMA to 100% of PEGMA. All polydispersity indices of the obtained copolymers are comprised between 1.11 and 1.30. The reactivity ratios have been determined by the extended Kelen−Tudos method (rDMAEMA = 0.93 and rPEGMA = 0.66). The behavior of the pH- and temperature-sensitive copolymers was studied in aqueous solution by measuring the lower critical solution temperature (LCST) by UV/vis spectroscopy. The measurements were performed at three different pH values (4, 7, and 10). At pH 7 and pH 10 it has been observed th...

Visualization of Flow-Aligned Type I Collagen Self-Assembly in Tunable pH Gradients

Collagen is a major component of the extracellular matrix that exhibits unique hierarchical organization at multiple length scales ranging from nano to macroscale. Despite numerous methods to create collagen-based biomaterials, the self-assembly process of collagen ex vivo is poorly understood. Here, we describe a system that uses a microfluidic method to investigate the dynamics of collagen self-assembly. A main inlet stream of semidilute soluble collagen-I is hydrodynamically focused by two side inlet streams, which gradually increases the pH in the main stream. This enables dynamic nonequilibrium investigation of the self-assembly process simultaneously at different positions and therefore different stages in the assembly process within the same system. The device is designed for in situ monitoring and characterization of collagen assembly using polarization microscopy and X-ray diffraction: the continuous extensional flow provides highly ordered phases of the macromolecules over a large distance in the outlet microchannel and allows for data collection without material damage. We further demonstrate that finite element method simulations provide a good description of our experimental results regarding the diffusive phenomena, flow profile, and pH distribution. Our approach has broad impact, since it provides a powerful means of controlling and investigating the dynamic self-assembly process of biomacromolecules.

Color tunable, ratiometric pH sensor for high and low pH values base on 9-(cycloheptatrienylidene)fluorene derivatives

Novel absorption and fluorescence pH sensors based on 9-(cycloheptatrienylidene)fluorene (9- CHF) derivatives have been prepared by well-known Suzuki coupling reaction. 2,7-Bis(4-hydroxyphenyl)-9- CHF ( 4), 2-(4-hydroxyphenyl)-7-(naphthanlen-1-yl)-9- CHF ( 6) have the abilities to respond at both low (−1.0 → 2.0) and high (8.2 → 13.1) pH values and can be utilized in absorption, fluorescence, and wavelength ratiometric methods. They might be complements of the glass pH electrodes for pH measurement. More interestingly, 4 exhibts violet emission in low pH value range, blue emission in middle pH value range, and green emission in high pH value range, which presents a color tunable pH sensor. ▪

Synthetic Macrocyclic Peptidomimetics as Tunable pH Probes for the Fluorescence Imaging of Acidic Organelles in Live Cells

Synthetic Macrocyclic Peptidomimetics as Tunable pH Probes for the Fluorescence Imaging of Acidic Organelles in Live Cells

Synthetic Macrocyclic Peptidomimetics as Tunable pH Probes for the Fluorescence Imaging of Acidic Organelles in Live Cells

Acid test: Macrocyclic compounds that comprise a 9,10-anthracene subunit linked by a C2-symmetric peptidomimetic chain (see formula) are useful as fluorescent probes in a pH range of biomedical interest. Changes in the size of the macrocycle (n=3,4,6,8) produce a shift in the pKa values. Experiments with live mouse macrophage cells show the selective localization of the probe in the acidic organelles (see differential interference contrast image).