Coacervation of Cationic Gemini Surfactant with <i>N</i>‑Benzoylglutamic Acid in Aqueous Solution

Coacervation of cationic gemini surfactant hexamethylene-1,6-bis­(dodecyldimethylammonium bromide) (12–6–12) with pH-sensitive <i>N</i>-benzoylglutamic acid (H₂Bzglu) has been investigated by potentiometric pH-titration, turbidity titration, dynamic light scattering (DLS), isothermal titration calorimetry (ITC), TEM, ¹H NMR, and light microscopy. Phase boundaries of the 12–6–12/H₂Bzglu mixture were obtained over the pH range from 2 to 9 and in the H₂Bzglu concentration range from 30.0 to 50.0 mM at pH 4.5. When the H₂Bzglu concentration is beyond 30.0 mM, the 12–6–12/H₂Bzglu mixed solution undergoes the phase transitions from soluble aggregate, to precipitate, coacervate, and soluble aggregate again as pH increases. The results indicate that coacervation occurs at extremely low 12–6–12 concentration and lasts over a wide surfactant range, and can be enhanced or suppressed by changing pH, 12–6–12/H₂Bzglu molar ratio and H₂Bzglu concentration. The coacervates present a disorderly connected lay structure. Coacervation only takes place at pH 4–5, where the aggregates are nearly charge neutralized, and a minimum H₂Bzglu concentration of 30.0 mM is required for coacervation. In this pH range, H₂Bzglu mainly exist as HBzglu^–. The investigations on intermolecular interactions indicate that the aggregation of 12–6–12 is greatly promoted by the strong electrostatic and hydrophobic interactions with the HBzglu^– molecules, and the interaction also promotes the formation of dimers, trimers, and tetramers of HBzglu^– through hydrogen bonds. The double chains of 12–6–12 and the HBzglu^– oligomers can play the bridging roles connecting aggregates. These factors endow the mixed system with a very high efficiency in generating coacervation

Regulation of eCB_mGluR.

<p>(a) Sample eIPSCs (each trace is the mean of 3) from the same U73122-loaded cell in the indicated conditions (U73122, 6 µM, also present in the bath). BL denotes the baseline response, and W, the response obtained after washing out DHPG. DHPG was applied 3 times at 20-min intervals starting ∼15–20 min after break-in. (b) Group data for experiments in (a); ^*p<0.01, one way repeated ANOVA; Scale: 20 ms/200 pA. (c) Sample eIPSCs (each trace is the mean of 3) response to 50 µM DHPG before and after repetitive DSI stimulation (1-s depolarizing steps were given at 12-s intervals continuously for 4 min). (d) Group data showing that eCB_mGluR was not affected by repetitive DSI stimulation. Scale: 20 ms/200 pA.</p

Antagonists of the primary catabolic enzyme for 2-AG, monoacylglycerol lipase (MAGL), prolong DSI.

<p>Diamonds indicate delivery of DSI-inducing voltage steps. Scale: 30 s/150 pA. (a) Bath application of MAGL inhibitors, JZL184 (1 µM) or OMDM-169 (2 µM), prolong DSI. (b) Group data showing recovery DSI in the presence of DMSO (Veh), JZL184, or OMDM-169. The DSI-inducing voltage step ended 1 s prior to time 0. The solid lines are best fitting single-exponential functions; the time constants of these functions were taken as the decay time constants (τ_decay) of DSI. (c) Group data showing increases in τ_decay of DSI in the indicated conditions. When applied for 40–120 min, JZL184 or OMDM-169, prolonged DSI; τ_decay was increased by ∼40% (DMSO: 13.9±1.1 s, n = 21; JZL184: 19.2±1.7 s, n = 15; OMDM-169: 20.4±1.6 s, n = 15; p<0.01, one way ANOVA).</p

Intracellular application of DAGL inhibitors reduces DSI to a greater extent than it reduces eCB_mGluR.

<p>(a) Intracellular infusion of OMDM-188 reduced DSI; each symbol represents averaged DSI values (3 trials) from one cell. Only data for 5 µM (n = 16) and 10 µM (n = 38) groups shown for clarity; both differ from Veh-In group, K-S test, p<0.01. (b) Group data. Includes results in (a), plus 2 µM (n = 6), 20 µM (n = 40) groups. ^* p<0.001, one-way ANOVA on ranks. (c) Sample continuous trace showing DSI trials and eIPSC suppression by eCB_mGluR. Scale: 2 min/200 pA. (d) Group data for experiments as in (c) with internal 5, 10 or 20 µM OMDM-188, or Veh only. DSI and eCB_mGluR were measured, and eCB_mGluR was plotted against DSI for each cell. For the cells (n = 28/35) within dotted oval, mean eIPSC reduction from baseline by DSI is 4.3±1.06%, mean eCB_mGluR eIPSC reduction is 49.0±2.32%. The straight line is a linear regression fit to the data for 10 and 20 µM DHPG (see text for discussion).</p

Use-dependent reduction of eCB_mGluR with internal DAGL inhibitor.

<p>(a) Sample eIPSCs (each trace is the mean of 3) from the same OMDM-188-loaded (20 µM in the pipette) cell in the indicated conditions. BL denotes the baseline response, and W, the response obtained after washing out DHPG. DHPG was applied 3 times at 20-min intervals starting ∼15–20 min after break-in. (c) As in (a) except that the 1^st DHPG application was given ∼40 min after break-in – i.e., at the same time as the 2^nd DHPG application in (a) – and the 2^nd one at 50–60 min after break-in. (e) As in (a), with vehicle only present in the internal solution. (b)(d)(f) Group data for experiments in (a), (c), and (e), respectively. ^*p<0.001, one way repeated ANOVA; Scale: 20 ms/200 pA.</p

External application of DAGL inhibitors blocks DSI.

<p>(a) Representative DSI trial. Downward deflections are eIPSCs evoked at 4-s intervals; DSI was evoked by a 3-s voltage step to 0 mV from the holding potential of -70 mV; depression of eIPSCs after a step is the period of DSI (see text). Scale: 24 s/200 pA. (b) Bath application of OMDM-188 (5 µM) or THL (10 µM) essentially abolished DSI; K-S tests, p<0.01. Note: values <0 represent eIPSCs that were greater than baseline amplitudes, not enhanced DSI. (c) Group data. ^* p<0.001, one way ANOVA on ranks. Vehicle, n = 20; OMDM-188, n = 34; THL, n = 35.</p

External application of DAGL inhibitors has minimal effects on eCB_mGluR.

<p>(a) Sample trace showing eIPSCs (downward deflections) and DSI trials (diamonds) in external OMDM-188, 5 µM. Note DSI is abolished despite continued suppression of eIPSCs by DHPG. (b) Sample eIPSCs (each trace is the mean of 3) from the same cell in external OMDM-188. BL denotes the baseline response, and W, the response obtained after washing out DHPG. DHPG was applied twice at 20-min intervals starting ∼15–20 min after break-in. (d) As in (b), with THL in the saline. (f) As in (b), with vehicle only in the saline. (c)(e)(g) Group data for experiments in (b), (d), and (f), respectively (paired-t-tests). OMDM-188-Out, n = 15, p<0.01; THL-Out, n = 13, p<0.05; Vehicle-Out, n = 8, p>0.5. Scale: 20 ms/200 pA.</p

Complementary X-ray, ellipsometry and neutron data from Non-lamellar lipid assembly at interfaces: controlling layer structure by responsive nanogel particles

Figure S1. Effect of temperature on the lattice parameter, a, of a cubic phase composed of GMO-50/DGMO (40/60 weight ratio) alone (open markers) or containing 10 wt% nanogel (black solid markers). Figure S2. SAXS data for the formulations of nanogels dispersed in lipids (85 wt % lipids composed of GMO-50/DGMO at a 40/60 weight ratio) with 15 wt % ethanol at 25 °C and 40 °C. Figure S3. Spectroscopic ellipsometry parameters, Δ (pink circles) and ψ (black triangles), as a function of wavelength for a film of GMO-50:DGMO (40:60 wt%) on silica. Figure S4. (A) Schematic representation of magnetic contrast surfaces used in this study. Figure S5. Neutron reflectivity data for a spin coated film of GMO-50:DGMO (60:40 wt% ratio) containing nanogel (10wt%) at (A) 25°C and (B) 40°C. Figure S6. Diffraction pattern extracted from the off-specular neutron reflectivity patterns in Figure 6 of lipid-only and lipid-nanogel layers at 25 °C and 40 °C