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Gayathri Mohanan Karthika S. Nair K. Madhavan Nampoothiri Harsha Bajaj 《Chemical science》2020,11(18):4669
Controlled design of giant unilamellar vesicles under defined conditions has vast applications in the field of membrane and synthetic biology. Here, we bio-engineer bacterial-membrane mimicking models of controlled size under defined salt conditions over a range of pH. A complex bacterial lipid extract is used for construction of physiologically relevant Gram-negative membrane mimicking vesicles whereas a ternary mixture of charged lipids (DOPG, cardiolipin and lysyl-PG) is used for building Gram-positive bacterial-membrane vesicles. Furthermore, we construct stable multi-compartment biomimicking vesicles using the gel-assisted swelling method. Importantly, we validate the bio-application of the bacterial vesicle models by quantifying diffusion of chemically synthetic amphoteric antibiotics. The transport rate is pH-responsive and depends on the lipid composition, based on which a permeation model is proposed. The permeability properties of antimicrobial peptides reveal pH dependent pore-forming activity in the model vesicles. Finally, we demonstrate the functionality of the vesicles by quantifying the uptake of membrane-impermeable molecules facilitated by embedded pore-forming proteins. We suggest that the bacterial vesicle models developed here can be used to understand fundamental biological processes like the peptide assembly mechanism or bacterial cell division and will have a multitude of applications in the bottom-up assembly of a protocell.Giant vesicle functional models mimicking a bacterial membrane under physiological conditions are constructed. 相似文献
136.
M. M. Taqui Khan S. A. Samad M. R. H. Siddiqui H. C. Bajaj G. Ramachandraiah 《Polyhedron》1991,10(23-24)
The interaction of molecular hydrogen with [Rh(PPh3)3]+ (1a) “immobilized” in the interlamellar spaces of montmorillonite resulted in the formation of a monohydrido complex, [RhIIH(PPh3)3] (2a), characterized by electrochemical data of the clay-loaded electrode, IR, EPR and hydrogen absorption studies. Heterogenized homogeneous catalytic hydrogenation of cyclohexene catalysed by 1a was investigated in the temperature range 283–313 K. The order of reaction with respect to cyclohexene and hydrogen concentration is fractional and first order with respect to catalyst concentration. Thermodynamic parameters ΔH0 and ΔS0 corresponding to the formation of the monohydrido species were found to be 18 kcal mol−1 and 61 e.u., respectively. The activation enthalpy, ΔH‡, and entropy, ΔS‡, for the hydrogenation of cyclohexene by the RhII—H complex in clay are more negative by about 2 kcal mol−1 and 7 e.u. compared to Wilkinson's catalyst, RhCl(PPh3)3 (1), in homogeneous solution. 相似文献
137.
Membrane formation from gemini pseudoglyceryl lipids bearing n-C14H29 and n-C16H33 chains has been reported. These lipid aggregates have been characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), high sensitivity differential scanning calorimetry (DSC), and Paldan fluorescence studies. The length of the spacer between the cationic ammonium headgroups has been varied from -(CH2)3- (propandiyl) to -(CH2)12- (dodecandiyl) in these lipids. All gemini lipids were found to generate stable suspensions in aqueous media. Electron microscopic studies revealed the smaller size of the gemini lipid aggregates as compared to their monomeric lipid counterparts. DLS measurements showed that the gemini lipid suspensions with a -(CH2)8- spacer length were bigger in size than that of other analogues. DSC studies suggest the unusual behavior of the gemini lipids bearing -(CH2)3- propanediyl spacer based lipids. These observations were consistent irrespective of the hydrocarbon chain lengths of the lipids. Paldan fluorescence based hydration studies showed that the hexadecyl chain based gemini lipid aggregates bearing a -(CH2)12- spacer were the most hydrated in their gel states among all the gemini lipid series investigated herein. 相似文献
138.
M.M. Bajaj 《Physics letters. A》1976,56(5):390-392
Self-diffusion process in EuB6 was studied using the pulsed gradient spin echo NMR technique. At 1.7 K, zero-field value of the self-diffusion parameter, k, was found to be (66 ± 4) × 10-6 (μs)-3, while that with 5 kG polarizing field turned out to be (3 ± 0.6) × 10-6 (μs)-3. 相似文献
139.
Hari C. Bajaj Surendra Prasad Radhey M. Naik Prem C. Nigam 《Transition Metal Chemistry》1991,16(5):511-517
Summary The kinetics and mechanism of ligand substitution reactions of tetraethylenepentamine nickel(II), Ni (Teren), and triethylenetetraamine nickel(II), Ni(Trien), with 4-(2-pyridylazo)resorcinol (parH2) have been studied spectrophotometrically at I=0.1 M (NaClO4) at 25°C. In both systems two distinct reaction steps are observed. The rapid first step follows the rate law d[Ni(Polyamine)(ParH2)]/dt=k1 [Ni(Polyamine)] [ParH2]. The formation of ternary complexes of Ni (Polyamine) with ParH2 has been investigated under second order equal concentration conditions. The values of second order rate constants for the Trien and Teren reactions are (2.1±0.2)×104 M–1s–1 and (7.8±0.6)×103 M–1s–1 respectively at pH=9.0, I=0.1 M and 25°C.The rate law for the second step may be written as d[Ni(Par)2]/dt=k2[Ni(Polyamine)(ParH2)]. Values of k2 for the Trien and Teren systems are (2.5±0.1)×10–4 s–1 and (4.76±0.3)×10–5 s–1 respectively. 相似文献
140.
Cover Picture: Ultra‐Low‐Field NMR Relaxation and Diffusion Measurements Using an Optical Magnetometer (Angew. Chem. Int. Ed. 37/2014) 下载免费PDF全文