l‑Histidine Salt-Bridged Monomer Preassembly and Polymerization-Induced Electrostatic Self-Assembly

Salt bridges are predominant in protein construction and stabilization, yet largely unexplored for polymer nanoparticle synthesis. We herein report the use of l-histidine salt bridges to drive monomer preassembly and two-dimensional electrostatic self-assembly in aqueous photo-RAFT polymerization. l-histidine salt bridges drive the monomer clustering nucleation, complex coacervation, and Coulombic stabilization, leading to the 2 nm ultrasmall clusters and coacervate droplets. Homopolymerization leads to a precision two-dimensional electrostatic self-assembly via a droplet-monolayer-multilayer transition, i.e., salt-bridged homo-polymerization-induced self-assembly (PISA). Block copolymerization does not disturb the “salt-bridged homo-PISA” mechanism. Enhanced Coulombic repulsion via seeded polymerization of charged monomers using as-achieved multilayer lamellae (seeds) yields supercharged 5 nm ultrathin monolayer lamellae with high colloidal stability upon dilution, salting, and long-term storage, urgently needed for bioapplications. This work opens up a new avenue to use amino acid salt bridges for PISA synthesis of biologically important, yet hitherto inaccessible, salt-resistant ultrathin polyelectrolyte complex nanomaterials

Thermally Activated Delayed Fluorescent Emitters Based on Cyanobenzene Exhibiting Fast Reverse Intersystem Crossing to Suppress the Efficiency Roll-Off

Thermally activated delayed fluorescent (TADF) materials exhibiting the fast reverse intersystem crossing (RISC) process are essential for improving the stability of organic light-emitting diodes (OLEDs). However, for most TADF emitters, the upconversion processes from the lowest triplet state (T1) to the lowest singlet state (S1) are still inefficient due to the low RISC (kRISC) rate below 105 s–1. Herein, we report two TADF molecules, 2DACz-mCN and 2DACz-oCN, that possess multiple donor units to minimize singlet–triplet energy splitting (ΔEST) and enhance the spin–orbit coupling matrix elements. Our work shows that the rate constants of RISC of 2DACz-mCN and 2DACz-oCN are as fast as ∼2.7 × 106 and ∼8.6 × 106 s–1, which are 1 order of magnitude higher than the other benzonitrile-based TADF molecules. The short delayed fluorescent lifetimes of ∼1.58 and ∼1.16 μs in doped films are achieved. The OLEDs by utilizing 2DACz-oCN as emitter exhibit green electroluminescence (EL) with CIE chromaticity coordinates of (0.28, 0.49) and high maximum quantum efficiency of ∼25.1% with the suppressed efficiency roll-off, which still remains ∼21% at the luminance of 1000 cd/m2

CaMKII Is Essential for the Function of the Enteric Nervous System

<div><h3>Background</h3><p>Ca²⁺/calmodulin-dependent protein kinases (CaMKs) are major downstream mediators of neuronal calcium signaling that regulate multiple neuronal functions. CaMKII, one of the key CaMKs, plays a significant role in mediating cellular responses to external signaling molecules. Although calcium signaling plays an essential role in the enteric nervous system (ENS), the role of CaMKII in neurogenic intestinal function has not been determined. In this study, we investigated the function and expression pattern of CaMKII in the ENS across several mammalian species.</p> <h3>Methodology/Principal Findings</h3><p>CaMKII expression was characterized by immunofluorescence analyses and Western Blot. CaMKII function was examined by intracellular recordings and by assays of colonic contractile activity. Immunoreactivity for CaMKII was detected in the ENS of guinea pig, mouse, rat and human preparations. In guinea pig ENS, CaMKII immunoreactivity was enriched in both nitric oxide synthase (NOS)- and calretinin-containing myenteric plexus neurons and non-cholinergic secretomotor/vasodilator neurons in the submucosal plexus. CaMKII immunoreactivity was also expressed in both cholinergic and non-cholinergic neurons in the ENS of mouse, rat and human. The selective CaMKII inhibitor, KN-62, suppressed stimulus-evoked purinergic slow EPSPs and ATP-induced slow EPSP-like response in guinea pig submucosal plexus, suggesting that CaMKII activity is required for some metabotropic synaptic transmissions in the ENS. More importantly, KN-62 significantly suppressed tetrodotoxin-induced contractile response in mouse colon, which suggests that CaMKII activity is a major determinant of the tonic neurogenic inhibition of this tissue.</p> <h3>Conclusion</h3><p>ENS neurons across multiple mammalian species express CaMKII. CaMKII signaling constitutes an important molecular mechanism for controlling intestinal motility and secretion by regulating the excitability of musculomotor and secretomotor neurons. These findings revealed a fundamental role of CaMKII in the ENS and provide clues for the treatment of intestinal dysfunctions.</p> </div

CaMKII is required for metabotropic purinergic signaling in the ENS.

<p>(A) Slow EPSPs were evoked by electrical stimulation to the interganglional fiber tract in guinea pig submucosal plexus. The CaMKII inhibitor KN-62 suppressed the slow EPSP in a reversible manner. (B) KN-62 also suppressed ATP-induced slow EPSP-like response in the same cell as shown in A. (C) The uniaxonal morphology of the recorded cells was revealed by staining biocytin injected into the cell through microelectrode. (D) Summary statistics of the effect of W-7 and KN-62 on stimulus-evoked slow EPSPs. (E) Summary statistics of the effect of W-7 and KN-62 on ATP-induced slow EPSP-like response.</p

CaMKII is required for neurogenic inhibition of colon motility.

<p>(A) KN-62 nearly abolished TTX-evoked contractile response in a mouse colon strip. The effect of KN-62 was partially reversible after about 1 hr washout. (B) Bath application of KN-62 also suppressed CCh-induced myogenic contraction in a reversible manner. (C) The inhibitory effect of KN-62 on TTX-induced response was significantly stronger than on CCh-induced contraction. ** p<0.01. (D) Representative Western Blot analysis shows that pretreatment with 3 µM KN-62 for 15 min dramatically decreased the p-CaMKII-IR in the myenteric plexus preparations of mouse colon. The total CaMKII-IR was comparable between tissue preparations with and without treatment with KN-62. β-actin was used as a loading control. (E) Schematic diagram illustrates the neurogenic and myogenic roles of CaMKII in controlling the colonic intestinal motility.</p

CaMKII is expressed by a subset of neurons in the ENS across multiple mammalian species.

<p>(A-C) Representative images illustrate that CaMKII-IR was localized in a subpopulation of rat myenteric neurons. Anti-Hu immunoreactivity was used to label all neurons. (D-F) Representative images show that CaMKII-IR was present in a subpopulation of anti-Hu-immunoreactive rat submucosal neurons. (G) The proportions of CaMKII-immunoreactive neurons in the myenteric plexus of multiple mammalian species. (H) The proportions of CaMKII-immunoreactive neurons in the submucosal plexus across multiple mammalian species.</p

Distribution of CaMKII in relation to chemical codes in both myenteric (A) and submucosal (B) plexuses of ileum among different mammalian species.

<p>Distribution of CaMKII in relation to chemical codes in both myenteric (A) and submucosal (B) plexuses of ileum among different mammalian species.</p

Localization and chemical coding of CaMKII in the ileal myenteric plexuses of guinea pig, rat, human and mouse.

<p>In guinea pig ileal myenteric plexus CaMKII-IR colocalized with NOS- (A), calretinin- (B) and NK1R- (C) IR. CaMKII-IR also colocalized with NOS- (D), calretinin - (E) and calbindin - (F) IR in rat ileal myenteric plexus. In human duodenal myenteric plexus CaMKII-IR colocalized with NOS- (G), calretinin- (H) and calbindin- (I) IR. In mouse ileal myenteric plexus CaMKII-IR also colocalized extensively with NOS- (J), calretinin- (K) and calbindin- (L) IR. Yellow color refers to overlapping images. Bar = 20 μm for all images.</p

Localization and chemical coding of CaMKII in rat, human and mouse submucosal plexuses.

<p>CaMKII-IR was localized in almost all VIP-immunoreactive neurons (A) and some ChAT-immunoreactive neurons (B) in rat submucosal plexus. In the mouse submucosal plexus, CaMKII-IR also colocalized extensively with VIP-IR (C) but much less with ChAT-IR (D). On the other hand, CaMKII-IR colocalized with both VIP-IR (E) and ChAT-IR (F) in human submucosal plexus. Yellow color refers to overlapping images. Bar = 20 μm for all images.</p

CaMKII is present in the guinea pig ENS.

<p>(A) Representative Western Blot analysis reveals the presence of CaMKII-IR in protein extracts of guinea pig myenteric and submucosal plexuses of both ileum and colon. p-CaMKII-IR was also present in the myenteric plexus. Calbindin (28 kD) which is only expressed by enteric neurons was used as a positive control. (B & C) Low magnification images illustrate that many guinea pig ileal myenteric neurons had CaMKII-IR. (D) CaMKII-IR was exclusively expressed by uniaxonal S-type myenteric neurons and present in both cell soma and nerve fibers. Bar = 20 μm.</p