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Biswas J.,Indian Institute of Science | Bajaj A.,Indian Institute of Science | Bajaj A.,Regional Center for Biotechnology | Bhattacharya S.,Indian Institute of Science | Bhattacharya S.,Chemical Biology Unit
Journal of Physical Chemistry B | Year: 2011

Two series of cholesterol-based cationic gemini lipids with and without hydroxyl functions at the headgroups possessing different lengths of polymethylene [-(CH2)n-] (n = 3, 4, 5, 6, 12) spacer have been synthesized. Each gemini lipid formed stable suspension in water. The suspensions of these gemini lipids in water were investigated using transmission electron microscopy, dynamic light scattering, zeta potential measurements and X-ray diffraction to characterize the nature of the individual aggregates formed therein. The aggregation properties of these gemini lipids in water were found to strongly depend upon the length of the spacer and the presence of hydroxyl group at the headgroup region. Lipoplex formation (DNA binding) and the release of the DNA from such lipoplexes were performed to understand the nature of interactions that prevail between these cationic cholesterol aggregates and duplex DNA. The interactions between such gemini lipids and DNA depend both on the presence of OH on the headgroups and the spacer length between the headgroups. Finally, we studied the effect of incorporation of each cationic gemini lipid into dipalmitoyl phosphatidylcholine vesicles using differential scanning calorimetry. The properties of the resulting mixed membranes were found again to depend upon the nature of the headgroup and the spacer chain length. © 2010 American Chemical Society. Source

Saha K.,University of Massachusetts Amherst | Bajaj A.,University of Massachusetts Amherst | Bajaj A.,Regional Center for Biotechnology | Duncan B.,University of Massachusetts Amherst | Rotello V.M.,University of Massachusetts Amherst
Small | Year: 2011

Surface recognition of biosystems is a critical component in the development of novel biosensors and delivery vehicles, and for the therapeutic regulation of biological processes. Monolayer-protected nanoparticles present a highly versatile scaffold for selective interaction with bio-macromolecules and cells. Through the engineering of the monolayer surface, nanoparticles can be tailored for surface recognition of biomolecules and cells. This review highlights recent progress in nanoparticle-bio-macromolecule/cellular interactions, emphasizing the effect of the surface monolayer structure on the interactions with proteins, DNA, and cell surfaces. The extension of these tailored interactions to hybrid nanomaterials, biosensing platforms, and delivery vehicles is also discussed. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Heesters B.A.,Program in Cellular and Molecular Medicine | Das A.,Program in Cellular and Molecular Medicine | Chatterjee P.,Regional Center for Biotechnology | Carroll M.C.,Program in Cellular and Molecular Medicine | Carroll M.C.,Harvard University
Molecular Immunology | Year: 2014

The factors that allow self-reactive B cells to escape negative selection and become activated remain poorly defined. In this review we describe recently published results in which a B cell receptor-knock-in mouse strain specific for nucleolar self-antigens was bred with mice deficient in complement C4 and discuss the implications for the lupus field. Absence of C4 leads to a breakdown in the elimination of autoreactive B cell clones at the transitional stage. This is characterized by a relative increase in their response to a range of stimuli, entrance into follicles and a greater propensity to form self-reactive germinal centers. In this review, a model is proposed in which, in the absence of complement C4, inappropriate clearance of apoptotic debris promotes chronic activation of myeloid cells and follicular dendritic cells, resulting in secretion of Type I interferon. This allows for the maturation and activation of self-reactive B cell clones leading to increased spontaneous formation of germinal centers and subsequent generation of autoantibodies. © 2014 Elsevier Ltd. Source

Bhattacharjee S.,University of Missouri | Bhattacharjee S.,Regional Center for Biotechnology | Garner C.M.,University of Missouri | Gassmann W.,University of Missouri
Frontiers in Plant Science | Year: 2013

The robustness of plant effector-triggered immunity is correlated with massive alterations of the host transcriptome. Yet the molecular mechanisms that cause and underlie this reprogramming remain obscure. Here we will review recent advances in deciphering nuclear functions of plant immune receptors and of associated proteins. Important open questions remain, such as the identities of the primary transcription factors involved in control of effector-triggered immune responses, and indeed whether this can be generalized or whether particular effector-resistance protein interactions impinge on distinct sectors in the transcriptional response web. Multiple lines of evidence have implicated WRKY transcription factors at the core of responses to microbe-associated molecular patterns and in intersections with effector-triggered immunity. Recent findings from yeast two-hybrid studies suggest that members of theTCP transcription factor family are targets of several effectors from diverse pathogens. Additional transcription factor families that are directly or indirectly involved in effector-triggered immunity are likely to be identified. © 2013 Bhattacharjee, Garner and Gassmann. Source

Sreekanth V.,Regional Center for Biotechnology | Bajaj A.,Regional Center for Biotechnology
Journal of Physical Chemistry B | Year: 2013

We have studied the interactions of three bile acid-tamoxifen conjugates, lithocholic acid-tamoxifen (LA-Tam1-Am), deoxycholic acid-tamoxifen (DCA-Tam2-Am), and cholic acid-tamoxifen (CA-Tam3-Am), possessing 1-3 tamoxifen molecules having an amine headgroup with model DPPC membranes and compared with N-desmethylated tamoxifen (TamNHMe) using DPH based fluorescence anisotropy, Prodan based hydration, and differential scanning calorimetry studies. DPH based anisotropy studies showed that bile acid-tamoxifen conjugates increase membrane fluidity, which strongly depends on the number of tamoxifen molecules conjugated to bile acid and the percentage of doping of bile acid-tamoxifen conjugates in the DPPC membranes. The order of membrane fluidity of the coliposomes from bile acid-tamoxifen conjugates and DPPC lipids in gel phase was found to be CA-Tam3-Am > DCA-Tam 2-Am > LA-Tam1-Am > TamNHMe. Incorporation of bile acid-tamoxifen conjugates showed an unusual complex behavior of membrane hydration, as evident from Prodan based hydration studies. Temperature dependent study showed incorporation of LA-Tam1-Am and DCA-Tam2-Am conjugates decreases membrane hydration with an increase in temperature up to the phase transition temperature (Tm). Differential scanning calorimetry studies showed a decrease in phase transition temperature (T m) upon an increase in the percentage of doping of TamNHMe and CA-Tam3-Am, whereas LA-Tam1-Am and DCA-Tam2-Am do not cause a major change in the phase transition temperature (Tm) of DPPC liposomes. These studies showed the differential behavior of bile acid-tamoxifen conjugates regulating the membrane fluidity, hydration, and phase transition of model membranes depending upon the percentage of doping and tamoxifen conjugation to bile acids. © 2013 American Chemical Society. Source

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