Adsorption of C₁–C₄ Alcohols in Zeolitic Imidazolate Framework-8: Effects of Force Fields, Atomic Charges, and Framework Flexibility

A molecular simulation study is reported for the adsorption of normal alcohols (methanol, ethanol, propanol, and butanol) in zeolitic imidazolate framework-8 (ZIF-8). The effects of force fields, atomic charges, and framework flexibility are systematically examined and compared with experimental data. Among three force fields (UFF, AMBER, and DREIDING), DREIDING has the best agreement with experiment. The atomic charges and framework flexibility are found to have negligible effects. The four alcohols exhibit S-shaped isotherms without hysteresis loop, as attributed to adsorption at different preferential sites. At a low pressure, cluster formation is observed near the organic linker (2-methylimidazolate) in ZIF-8; with increasing pressure, cage-filling occurs in the large sodalite cage. The interaction between alcohol and ZIF-8 framework is enhanced as the chain length of alcohol increases; thus, the isosteric heat of adsorption rises with chain length. The simulation study provides microscopic insight into alcohol adsorption in ZIF-8, which is useful for quantitative understanding of adsorption mechanism in other ZIFs and nanoporous materials

ER redox state monitored by FACS analysis in response to DTT treatment.

<p>(A) FACS plots from a representative experiment of untreated and DTT (5 mM) treated INS-1 cells (GRP78mCherry/eroGFP # 15/5). Scatter plot: forward scatter (FSC) vs. side scatter (SSC) and gated populations are represented (top left and top right panel); typical fluorescence emission of INS-1 (GRP78mCherry/eroGFP # 15/5) cells before and after addition of DTT (5 mM) for 30 min (lower left and right panels); fluorescence intensities as areas for eroGFP (488 nm), eroGFP (405 nm) and mCherry are shown. (B) eroGFP ratio (from n = 9 experiments) in cells before and after addition of 5 mM DTT (C) Ethidium bromide stained agarose gel of unspliced (uXBP-1) and spliced (sXBP-1) XBP-1 cDNA obtained by RT-PCR of total RNA of untreated and DTT treated cells. (D) eroGFP ratio (from n = 3 experiments) in cells before and after addition of 0.1 mM H₂O₂ at the indicated times.</p

OASIS/CREB3L1 Is Induced by Endoplasmic Reticulum Stress in Human Glioma Cell Lines and Contributes to the Unfolded Protein Response, Extracellular Matrix Production and Cell Migration

<div><p>OASIS is a transcription factor similar to ATF6 that is activated by endoplasmic reticulum stress. In this study we investigated the expression of OASIS in human glioma cell lines and the effect of OASIS knock-down on the ER stress response and cell migration. OASIS mRNA was detected in three distinct glioma cell lines (U373, A172 and U87) and expression levels were increased upon treatment with ER stress-inducing compounds in the U373 and U87 lines. OASIS protein, which is glycosylated on Asn-513, was detected in the U373 and U87 glioma lines at low levels in control cells and protein expression was induced by ER stress. Knock-down of OASIS in human glioma cell lines resulted in an attenuated unfolded protein response to ER stress (reduced GRP78/BiP and GRP94 induction) and decreased expression of chondroitin sulfate proteoglycan extracellular matrix proteins, but induction of the collagen gene Col1a1 was unaffected. Cells in which OASIS was knocked-down exhibited altered cell morphology and reduced cell migration. These results suggest that OASIS is important for the ER stress response and maintenance of some extracellular matrix proteins in human glioma cells.</p> </div

eroGFP ratio in dispersed rat islet cells.

<p>(A) eroGFP ratio in dispersed rat islet cells transduced with eroGFP adenovirus (24 h), then treated with vehicle or treated with Tg (1 µM) for 3 h. Data was obtained by confocal imaging and image analysis. (B) eroGFP ratio in rat islet cells before and after addition of 5 mM DTT for 10 min, obtained by confocal imaging and image analysis. eroGFP ratios are represented as the mean (±SEM) with a minimum of 50 cells analyzed per condition. *Denotes significance from untreated cells by Student <i>t</i>-test (<i>p</i><0.05).</p

eroGFP ratio in response to ER stress induced by DL-homocysteine.

<p>(A) eroGFP ratio (from n = 3 experiments) in INS-1 cells (GRP78mCherry/eroGFP # 15/5) treated or not with 5 mM DL-homocysteine for the times indicated obtained by FACS analysis. (B) Ethidium bromide–stained agarose gel of unspliced (uXBP-1) and spliced (sXBP-1) XBP-1 cDNA obtained by RT-PCR of total RNA of cells treated or not with 5 mM DTT or 5 mM DL-homocysteine for indicated times.</p

Analyses of INS-1 (GRP78mCherry/eroGFP # 15/5) cells under conditions of pharmacologically-induced ER stress.

<p>(A) eroGFP ratio of cells treated with thapsigargin (Tg) or tunicamycin (Tm) for the indicated times obtained by confocal imaging and image analysis. (B) FACS plots from a representative experiment of untreated cells or of cells treated with 2 µg/ml Tm for 16 h. Scatter plot: forward scatter (FSC) vs. side scatter (SSC) and gated population are represented (top left and top right panel); typical fluorescence emission of INS-1 (GRP78mCherry/eroGFP # 15/5) cells before and after incubation with Tm (2 µg/ml) for 16 h (lower left and right panels); fluorescence intensities as areas for eroGFP (488 nm), eroGFP (405 nm) and mCherry are shown. (C) eroGFP ratio (from n = 3 experiments) in cells treated with vehicle or treated with Tm (2 µg/ml) for 16 h obtained by FACS analysis. (D) eroGFP ratio of cells treated with Tg (1 µM) for 1 h or 4 h analyzed by FACS analysis, normalized to vehicle control. (E) Ethidium bromide stained agarose gel of unspliced (uXBP-1) and spliced (sXBP-1) XBP-1 cDNA obtained by RT-PCR of total RNA of cells after treatment with Tg (1 h and 4 h) or Tm (16 h). (F) Relative GRP78 mRNA level as determined by real-time PCR. Total RNA was isolated from GRP78mCherry/eroGFP #15/5 cells untreated, treated with DTT (5 mM) for 30 min, treated with vehicle (DMSO) for 16 h or Tm (2 µg/ml) for 16 h and real-time PCR analysis was performed to determine GRP78 mRNA expression. *Denotes significance at <i>p</i><0.05 (ANOVA).</p

OASIS mRNA is expressed in human glioma cell lines.

<p>(A) RNA was isolated lines human glioma cell lines U373, A172, U87 and rat C6 glioma cell lines and OASIS cDNA was amplified by RT-PCR. An ∼1.5 kbp OASIS cDNA was amplified in all cell lines. (B) Human glioma cell lines U373, A172, U87 were treated or not with thapsigargin (TG, 1 µM 18 h) or tunicamycin (TM, 2 µg/ml 18 h). Real time PCR analysis of OASIS mRNA expression relative to cellular β-actin mRNA. Result is from N = 3 independent experiments for each cell line. Bars are SEM.</p

eroGFP ratio in cells treated with FFAs and high glucose.

<p>(A) eroGFP ratio of INS-1 cells (GRP78mCherry/eroGFP # 15/5) treated with palmitate and oleate for 6 h and 16 h obtained by FACS analysis normalized to BSA control. (B) Ethidium bromide–stained agarose gel of unspliced (uXBP-1) and spliced (sXBP-1) XBP-1 cDNA obtained by RT-PCR of total RNA of untreated cells, BSA treated cells and cells after treatment with palmitate (6 h and 16 h). (C) eroGFP ratio of cells under basal glucose (5 mM), acute (25 mM glucose for 2 h) and chronic high glucose (25 mM glucose for 48 h), obtained by FACS analysis. eroGFP ratios are normalized to control (untreated) cells in RPMI media (11.1 mM glucose).</p

OASIS knock-down perturbs U373 cell migration.

<p>(A) U373 cells transfected with 100 nM control (GFP) or OASIS siRNAs for 72 h before scratching the 90% confluent cell monolayers. The cells were then incubated for the indicated times and DIC images were obtained. The approximate cell migration is indicated by the white lines. The images were analyzed by ImageJ and the % wound area was quantified (B) (*p<0.05; OASIS siRNA vs. control siRNA, n = 3). Note the almost complete healing of the wound in control cells and poor migration of cells in which OASIS was knocked-down.</p

Response of cells to various concentrations of DTT over time.

<p>(A) eroGFP ratio (from n = 4 experiments) in INS-1 cells (GRP78mCherry/eroGFP # 15/5) treated or not with 0.1 mM DTT, 0.5 mM DTT and 5 mM DTT for the indicated times obtained by FACS analysis. * Denotes significance from untreated cells by Student <i>t</i>-test (<i>p</i><0.05). (B) Ethidium bromide stained agarose gel of unspliced (uXBP-1) and spliced (sXBP-1) XBP-1 cDNA obtained by RT-PCR of total RNA of cells treated with 0.1 mM DTT, 0.5 mM DTT and 5 mM DTT at the indicated times.</p