Porous Nitrogen Rich Cadmium-Tetrazolate Based Metal Organic Framework (MOF) for H₂ and CO₂ Uptake

The highly porous nitrogen rich metal organic framework [Cd3(4-TP)6] (Cd-4TP-1) was synthesized solvothermally from the predesigned organic building block 4-tetrazole pyridine (4-TP) and Cd(II) as metal center using DMF as solvent. Cd-4TP-1 has a three-dimensional porous architecture where all the binding sites of Cd(II) are exclusively occupied by the nitrogen atoms from the μ2-tetrazolyl group or the pyridyl functionality of the 4-TP ligands. Cd-4TP-1 has Brunauer–Emmett–Teller (BET) and Langmuir surface areas of 472.2 and 728.6 m2/g, respectively, and shows 1.1 wt % H2 (77 K) and 2.7 mmol/g CO2 uptake (273 K)

Porous Nitrogen Rich Cadmium-Tetrazolate Based Metal Organic Framework (MOF) for H₂ and CO₂ Uptake

The highly porous nitrogen rich metal organic framework [Cd3(4-TP)6] (Cd-4TP-1) was synthesized solvothermally from the predesigned organic building block 4-tetrazole pyridine (4-TP) and Cd(II) as metal center using DMF as solvent. Cd-4TP-1 has a three-dimensional porous architecture where all the binding sites of Cd(II) are exclusively occupied by the nitrogen atoms from the μ2-tetrazolyl group or the pyridyl functionality of the 4-TP ligands. Cd-4TP-1 has Brunauer–Emmett–Teller (BET) and Langmuir surface areas of 472.2 and 728.6 m2/g, respectively, and shows 1.1 wt % H2 (77 K) and 2.7 mmol/g CO2 uptake (273 K)

Porous Nitrogen Rich Cadmium-Tetrazolate Based Metal Organic Framework (MOF) for H₂ and CO₂ Uptake

The highly porous nitrogen rich metal organic framework [Cd3(4-TP)6] (Cd-4TP-1) was synthesized solvothermally from the predesigned organic building block 4-tetrazole pyridine (4-TP) and Cd(II) as metal center using DMF as solvent. Cd-4TP-1 has a three-dimensional porous architecture where all the binding sites of Cd(II) are exclusively occupied by the nitrogen atoms from the μ2-tetrazolyl group or the pyridyl functionality of the 4-TP ligands. Cd-4TP-1 has Brunauer–Emmett–Teller (BET) and Langmuir surface areas of 472.2 and 728.6 m2/g, respectively, and shows 1.1 wt % H2 (77 K) and 2.7 mmol/g CO2 uptake (273 K)

Correction to Porous Nitrogen Rich Cadmium-Tetrazolate Based Metal Organic Framework (MOF) for H₂ and CO₂ Uptake

Correction to Porous Nitrogen Rich Cadmium-Tetrazolate Based Metal Organic Framework (MOF) for H₂ and CO₂ Uptak

Mechanochemical Synthesis of Amide Functionalized Porous Organic Polymers

Two porous organic polymers decorated with the amide functionality were synthesized mechanochemically and their properties were compared with the ones prepared by conventional solution mediated method. All the POPs were subjected to gas and water vapor sorption studies. The mechanochemically synthesized POPs have less surface area and show moderate adsorption properties compared to the solution mediated POPs. The amide based POPs show remarkable stability in water and concentrated acids

Correction to Porous Nitrogen Rich Cadmium-Tetrazolate Based Metal Organic Framework (MOF) for H₂ and CO₂ Uptake

Correction to Porous Nitrogen Rich Cadmium-Tetrazolate Based Metal Organic Framework (MOF) for H₂ and CO₂ Uptak

Conformational Transition in Signal Transduction: Metastable States and Transition Pathways in the Activation of a Signaling Protein

Signal transduction is of vital importance to the growth and adaptation of living organisms. The key to understand mechanisms of biological signal transduction is elucidation of the conformational dynamics of its signaling proteins, as the activation of a signaling protein is fundamentally a process of conformational transition from an inactive to an active state. A predominant form of signal transduction for bacterial sensing of environmental changes in the wild or inside their hosts is a variety of two-component systems, in which the conformational transition of a response regulator (RR) from an inactive to an active state initiates responses to the environmental changes. Here, RR activation has been investigated using RR468 as a model system by extensive unbiased all-atom molecular dynamics (MD) simulations in explicit solvent, starting from snapshots along a targeted MD trajectory that covers the conformational transition. Markov state modeling, transition path theory, and geometric analyses of the wealth of the MD data have provided a comprehensive description of the RR activation. It involves a network of metastable states, with one metastable state essentially the same as the inactive state and another very similar to the active state that are connected via a small set of intermediates. Five major pathways account for >75% of the fluxes of the conformational transition from the inactive to the active-like state. The thermodynamic stability of the states and the activation barriers between states are found, to identify rate-limiting steps. The conformal transition is initiated predominantly by movements of the β3α3 loop, followed by movements of the β4α4-loop and neighboring α4 helix region, and capped by additional movements of the β3α3 loop. A number of transient hydrophobic and hydrogen bond interactions are revealed, and they may be important for the conformational transition

Functionalization and Isoreticulation in a Series of Metal–Organic Frameworks Derived from Pyridinecarboxylates

The partially fluorinated metal–organic frameworks (F-MOFs) have been constructed from 3-fluoro-4-pyridinecarboxylic acid and <i>trans</i>-3-fluoro-4-pyridineacrylic acid linkers using Mn²⁺, Co²⁺, and Cd²⁺ metals via the solvothermal method, which show isostructural isomerism with their nonfluorinated counterparts synthesized using 4-pyridinecarboxylic acid and <i>trans</i>-4-pyridineacrylic acid, respectively. The simultaneous effect of partial fluorination and isoreticulation on structure and H₂ adsorption has been studied systematically in isostructural nonfluorinated and partially fluorinated MOFs, which shows that the increment in the hydrogen uptake properties in F-MOFs is not a universal phenomenon but is rather system-specific and changes from one system to another

Helical Water Chain Mediated Proton Conductivity in Homochiral Metal–Organic Frameworks with Unprecedented Zeolitic <i>unh</i>-Topology

Four new homochiral metal–organic framework (MOF) isomers, [Zn(l-LCl)(Cl)](H2O)2 (1), [Zn(l-LBr)(Br)](H2O)2 (2), [Zn(d-LCl)(Cl)](H2O)2 (3), and [Zn(d-LBr)(Br)](H2O)2 (4) [L = 3-methyl-2-(pyridin-4-ylmethylamino)butanoic acid], have been synthesized by using a derivative of l-/d-valine and Zn(CH3COO)2·2H2O. A three-periodic lattice with a parallel 1D helical channel was formed along the crystallographic c-axis. Molecular rearrangement results in an unprecedented zeolitic unh-topology in 1–4. In each case, two lattice water molecules (one H-bonded to halogen atoms) form a secondary helical continuous water chain inside the molecular helix. MOFs 1 and 2 shows different water adsorption properties and hence different water affinity. The arrangement of water molecules inside the channel was monitored by variable-temperature single-crystal X-ray diffraction, which indicated that MOF 1 has a higher water holding capacity than MOF 2. In MOF 1, water escapes at 80 °C, while in 2 the same happens at a much lower temperature (∼40 °C). All the MOFs reported here shows reversible crystallization by readily reabsorbing moisture. In MOFs 1 and 2, the frameworks are stable after solvent removal, which is confirmed by a single-crystal to single-crystal transformation. MOFs 1 and 3 show high proton conductivity of 4.45 × 10–5 and 4.42 × 10–5 S cm–1, respectively, while 2 and 4 shows zero proton conductivity. The above result is attributed to the fact that MOF 1 has a higher water holding capacity than MOF 2

Conformational Transition of Response Regulator RR468 in a Two-Component System Signal Transduction Process

Signal transduction can be accomplished via a two-component system (TCS) consisting of a histidine kinase (HK) and a response regulator (RR). In this work, we simulate the response regulator RR468 from Thermotoga maritima, in which phosphorylation and dephosphorylation of a conserved aspartate residue acts as a switch via a large conformational change concentrated in three proximal loops. A detailed view of the conformational transition is obscured by the lack of stability of the intermediate states, which are difficult to detect using common structural biology techniques. Molecular dynamics (MD) trajectories of the inactive and active conformations were run, and show that the inactive (or active) trajectories do not exhibit sampling of the active (or inactive) conformations on this time scale. Targeted MD (TMD) was used to generate trajectories that span the inactive and active conformations and provide a view of how a localized event like phosphorylation can lead to conformational changes elsewhere in the protein, especially in the three proximal loops. The TMD trajectories are clustered to identify stages along the transition path. Residue interaction networks are identified that point to key residues having to rearrange in the process of transition. These are identified using both hydrogen bond analysis and residue interaction strength measurements. Potentials of mean force are generated for key residue rearrangements to ascertain their free energy barriers. We introduce methods that attempt to extrapolate from one conformation to the other and find that the most fluctuating proximal loop can transit part way from one to the other, suggesting that this conformational information is embedded in the sequence