Air-Stable PbSe Nanocrystals Passivated by Phosphonic Acids

We developed a new chemical strategy to enhance the stability of lead selenide nanocrystals (PbSe NCs) against oxidation through the surface passivation by P–O– moieties. In the synthesis of PbSe NCs, tris­(diethyl­amino)­phosphine (TDP) selenide (Se) was used as a Se precursor, and the resulting PbSe NCs withstood long-term air exposure while showing nearly no sign of oxidation. Nuclear magnetic resonance (NMR) spectroscopy reveals that TDP derivatives passivate the surface of PbSe NC. Through a series of ligand cleavage reactions, we found that the TDP derivatives are bound on NC surface through the P–O– moiety. Based on such understanding, it turned out that direct addition of various PAs during the synthesis of PbSe NCs also results in the NCs whose absorption spectrum remains nearly intact after air exposure for weeks. The P–O– moieties render the NCs stable in the operation of field effect transistors, suggesting that our findings can enable the use of air stable PbSe NCs in wider array of optoelectronic applications

Modulation of the NF-kB signaling pathway by MLB.

<p>(A) Western blotting was performed for p-ERK, p-p38, p-JNK, ERK, p-38, and JNK in the cytoplasmic extracts of aged rat skin. (B) Western blotting was performed for p-ERK, p-p38, p-JNK, ERK, p-38, and JNK in the cytoplasmic extracts of UVB-irradiated human skin fibroblasts.</p

Modulation of MMP expression in aged rat skin and in UVB-irradiated human skin fibroblasts by MLB.

<p>(A) Western blot analysis was performed to assess MMP-9, MMP-12, and MMP-13 protein levels in the cytosolic extracts of the skins of aged rats. (B) Western blotting was performed to asses MMP-2, MMP-3, MMP-9, MMP-12, and MMP-13 levels in the cytoplasmic extracts of UVB-irradiated human skin fibroblasts. (C) Gelatinase and collagenase1 activities were assessed in aged rat skin by zymography. Gelatin zymography was used for MMP-2 (72 kDa) and MMP-9 (92 kDa), and collagen zymography was used for MMP-1 (52 kDa).</p

Possible anti-wrinkle mechanism of MLB.

<p>AP-1, activator protein 1; COX-2, cyclooxygenase-2; ERK, extracellular regulated signal kinase; iNOS, inducible nitric oxide synthase; JNK, c-Jun N-terminal kinases; MAPK, Mitogen-activated protein kinase; MMP, matrix metalloproteinase; ROS, reactive oxygen species; UVB, ultra violet B.</p

Inhibition of NF-kB-dependant genes by MLB.

<p>(A) Western blotting was used to assess the expressions of the NF-kB dependent genes COX-2 and iNOS in aged rat skin. (B) Western blotting was used to assess the expressions of the NF-kB dependent genes COX-2 and iNOS in UVB-irradiated human skin fibroblasts.</p

Effects of MLB on type I procollagen level in aged rat skin and UVB-irradiated human skin fibroblasts.

<p>(A) Western blotting was performed on cytoplasmic extracts of aged rat skin. (B) Cultured human fibroblasts were pretreated with MLB and caffeic acid, and exposed to 30 mJ/cm² of UVB. Western blotting was performed on cytoplasmic extracts of UVB-irradiated human skin fibroblasts. (C) Cultured human fibroblasts were pretreated with MLB and exposed to 30 mJ/cm² of UVB. Type I procollagen levels were analyzed by ELISA. Significances were determined using one-factor ANOVA: *p<0.05 vs. UVB-irradiated controls.</p

Structure of MLB from <i>Salvia miltiorrhiza</i> BUNGE.

<p>Structure of MLB from <i>Salvia miltiorrhiza</i> BUNGE.</p

Changes in AP-1 levels caused by MLB in aged rat skin and UVB-irradiated human skin fibroblasts.

<p>(A) Western blotting was used to assess nuclear cJun, cFOS, and p-cJun protein levels in aged rat skin. (B) Western blotting was used to assess nuclear cJun, cFOS, and p-cJun protein levels in UVB-irradiated human skin fibroblasts.</p

Changes in nuclear NF-κB levels caused by MLB in aged rat skin and UVB-irradiated human skin fibroblasts.

<p>(A) Western blotting was performed to assess nuclear p65 (Ser276), p65 (Ser536), Ac-p65, and p65 protein levels in aged rat skin. (B) Western blotting was performed to assess nuclear p65 (Ser276), p65 (Ser536), Ac-p65, and p65 protein levels in UVB-irradiated human skin fibroblasts.</p

Heptadecane suppressed the age-related activations of NIK/IKK and MAPKs.

<p>Western blot on renal cytoplasmic extracts (40 µg protein) from young, aged, and aged rats fed heptadecane. (A) Phosphorylations of P38 and JNK are designated p-p38 and p-JNK1/2. (B) Phosphorylations of NIK and IKK are designated p-NIK and p-IKKα/β. (C) Phosphorylations of MEK1/2 and ERK1/2 were detected using antibodies of p-MEK1/2 and p-ERK1/2. One representative blot of each protein from three experiments that yielded similar results is shown. Young rats (9 months of age) and aged (20 months of age) were utilized. Heptadecane was fed to aged rats at 2 mg or 4 mg/Kg per day for 10 days.</p