A note on proof of Gordon's Conjecture

Kun Du 대한수학회 2018 대한수학회보 Vol.55 No.3

In this paper, we show a proof of Gordon's Conjecture by using Qiu's labels and two new labels.

Biomimetic Designing of Functional Silk Nanotopography Using Self-assembly

Kundu, Banani,Eltohamy, Mohamed,Yadavalli, Vamsi K.,Kundu, Subhas C.,Kim, Hae-Won American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.42

<P>In nature inorganic organic building units create multifunctional hierarchical architectures. Organic silk protein is particularly attractive in this respect because of its micro-nanoscale structural blocks that are attributed to sophisticated hierarchical assembly imparting flexibility and compressibility to designed biohybrid materials. In the present study, aqueous silk fibroin is assembled to form nano/microtopography on inorganic silica surface via a facile diffusion-limited aggregation process. This process is driven by electrostatic interaction and only possible at a specified aminated surface chemistry. The self-assembled topography depends on the age and concentration of protein solution as well as on the surface charge distribution of the template. The self-assembled silk trails closely resemble natural cypress leaf architecture, which is considered a structural analogue of neuronal cortex. This assembled surface significantly enhances anchorage of neuronal cell and cytoskeletal extensions, providing an effective nano/microtopographical cue for cellular recognition and guidance.</P>

Epigallocatechin Gallate Inhibits Phorbol Ester-Induced Activation of NF- B and CREB in Mouse Skin: Role of p38 MAPK

KUNDU, J. K.,SURH, Y.-J. Wiley (Blackwell Publishing) 2007 Annals of the New York Academy of Sciences Vol.1095 No.1

<P>The modulation of intracellular signaling network involved in an inappropriate expression of cyclooxygenase-2 (COX-2) is a pragmatic approach for chemoprevention with a wide variety of dietary phytochemicals. Epigallocatechin gallate (EGCG), a major green tea polyphenol, is one of the most extensively investigated chemopreventive agents. Our previous study revealed that EGCG inhibited expression of COX-2 and activation of mitogen-activated protein kinases (MAPKs) in mouse skin stimulated with a prototype tumor promotor 12-O-tetradecanoylphorbol-13-acetate (TPA). This study was aimed at identifying transcription factors as molecular targets of EGCG in downregulating COX-2 expression. We found that EGCG inhibited TPA-induced DNA binding of NF-kappaB and CREB in mouse skin in vivo. EGCG also suppressed TPA-induced phosphorylation and subsequent degradation of IkappaBalpha, and prevented nuclear translocation of p65. We also examined whether extracellular signal-regulated protein kinase (ERK) and p38 MAPK, which are known to regulate activation of NF-kappaB, can also modulate CREB DNA binding. Pretreatment with U0126 and SB203580, pharmacological inhibitors of ERK and p38 MAPK, respectively, showed that SB203580, but not U0126, attenuated TPA-induced CREB DNA binding in mouse skin. Taken together, EGCG inhibited TPA-induced DNA binding of NF-kappaB and CREB by blocking activation of p38 MAPK, which may provide a molecular basis of COX-2 inhibition by EGCG in mouse skin in vivo.</P>

Nrf2-Keap1 Signaling as a Potential Target for Chemoprevention of Inflammation-Associated Carcinogenesis

Kundu, Joydeb Kumar,Surh, Young-Joon Springer-Verlag 2010 Pharmaceutical research Vol.27 No.6

A cobalt(<small>II</small>) iminoiodane complex and its scandium adduct: mechanistic promiscuity in hydrogen atom abstraction reactions

Kundu, Subrata,Chernev, Petko,Engelmann, Xenia,Chung, Chan Siu,Dau, Holger,Bill, Eckhard,England, Jason,Nam, Wonwoo,Ray, Kallol The Royal Society of Chemistry 2016 Dalton Transactions Vol.45 No.37

<P>In addition to oxometal [Mn+=O] and imidometal [Mn+=NR] units, transient metal-iodosylarene [M(n- 2)+-O=IPh] and metal-iminoiodane [M(n- 2)+-N(R)=IPh] adducts are often invoked as a possible 'second oxidant' responsible for the oxo and imido group transfer reactivity. Although a few metal-iodosylarene adducts have been recently isolated and/or spectroscopically characterized, metal-iminoiodane adducts have remained elusive. Herein, we provide UV-Vis, EPR, NMR, XAS and DFT evidence supporting the formation of a metal-iminoiodane complex 2 and its scandium adduct 2-Sc. 2 and 2-Sc are reactive toward substrates in the hydrogen-atom and nitrene transfer reactions, which confirm their potential as active oxidants in metal-catalyzed oxidative transformations. Oxidation of para-substituted 2,6-di-tert-butylphenols by 2 and 2-Sc can occur by both coupled and uncoupled proton and electron transfer mechanisms; the exact mechanism depends on the nature of the para substituent.</P>

Water Structure at the Lipid Multibilayer Surface: Anionic Versus Cationic Head Group Effects

Kundu, Achintya,Kwak, Kyungwon,Cho, Minhaeng American Chemical Society 2016 The Journal of physical chemistry B Vol.120 No.22

<P>Membrane water interface is a potential reaction site for many biochemical reactions. Therefore, a molecular level understanding of water structure and dynamics that strongly depend on the chemical structure of lipid is prerequisite for elucidating the role of water in biological reactions on membrane surface. Recently, we carried out femtosecond infrared pump probe studies of water structure and dynamics at multibilayer surfaces of zwitterionic phosphatidylcholine-analogue lipid (J. Phys. Chem. Lett. 2016, 7, 741). Here, to further elucidate the anionic and cationic headgroup effects on water, we study vibrational dynamics of water on lipid multibilayers formed by anionic phospho-glycerol lipid molecules as well as by cationic choline-derivatized lipid molecules. We observed two significantly different vibrational lifetime components (very fast 0.5 ps and slow 1.9 ps) of the OD stretch mode of HOD molecules at the negatively charged phospho-lipid multibilayer whereas only one vibrational lifetime component (1.6 ps) was observed at the positively charged choline-derivatized lipid multibilayer. From the detailed analyses about the vibrational energy and rotational relaxations of HOD molecules in lipid multibilayers composed of anionic lipid with phosphate and cationic lipid without phosphate, the role of phosphate group in structuring water molecules at phospholipid membrane interface is revealed.</P>

Environmentally benign and cost-effective synthesis of water soluble red light emissive gold nanoclusters: selective and ultra-sensitive detection of mercuric ions

Kundu, Aniruddha,Park, Byeongho,Ray, Chaiti,Oh, Juyeong,Jun, Seong Chan The Royal Society of Chemistry 2019 NEW JOURNAL OF CHEMISTRY Vol.43 No.2

<P>Heavy metal pollution is a potential threat because it exerts severe harmful effects on the environment and human health. Hence, the rational design and fabrication of fluorescent probes for the simple, selective, and sensitive detection of heavy metal ions are of great significance. In this article, we have reported an environmentally benign, green and cost-effective approach for the synthesis of red luminescent gold nanoclusters (AuNCs) using wheat flour as the stabilizing and capping agent. The resultant AuNCs have been characterized by several spectroscopic and microscopic techniques. We have achieved a high quantum yield (9.02%) for the red fluorescent AuNCs, with a maximum emission wavelength of ∼640 nm under 370 nm excitation. We have successfully applied the synthesized AuNCs for the nanomolar detection of Hg<SUP>2+</SUP> in an aqueous medium <I>via</I> selective fluorescence quenching of the AuNCs in the presence of several other metal ions. We have attained a limit of detection (LOD) as low as 7 nM for Hg<SUP>2+</SUP> and the selectivity of detection is attributed to the specific interaction between the Hg<SUP>2+</SUP> ions and the Au<SUP>+</SUP> ions present in the AuNCs.</P>

Alcohol and Temperature Induced Conformational Transitions in Ervatamin B: Sequential Unfolding of Domains

Kundu, Suman,Sundd, Monica,Jagannadham, Medicherla V. Korean Society for Biochemistry and Molecular Biol 2002 Journal of biochemistry and molecular biology Vol.35 No.2

The structural aspects of ervatamin B have been studied in different types of alcohol. This alcohol did not affect the structure or activity of ervatamin B under neutral conditions. At a low pH (3.0), different kinds of alcohol have different effects. Interestingly, at a certain concentration of non-fluorinated, aliphatic, monohydric alcohol, a conformational switch from the predominantly $\alpha$-helical to $\beta$-sheeted state is observed with a complete loss of tertiary structure and proteolytic activity. This is contrary to the observation that alcohol induces mostly the $\alpha$helical structure in proteins. The O-state of ervatamin B in 50% methanol at pH 3.0 has enhanced the stability towards GuHCl denaturation and shows a biphasic transition. This suggests the presence of two structural parts with different stabilities that unfold in steps. The thermal unfolding of ervatamin B in the O-state is also biphasic, which confirms the presence of two domains in the enzyme structure that unfold sequentially. The differential stabilization of the structural parts may also be a reflection of the differential stabilization of local conformations in methanol. Thermal unfolding of ervatamin B in the absence of alcohol is cooperative, both at neutral and low pH, and can be fitted to a two state model. However, at pH 2.0 the calorimetric profiles show two peaks, which indicates the presence of two structural domains in the enzyme with different thermal stabilities that are denatured more or less independently. With an increase in pH to 3.0 and 4.0, the shape of the DSC profiles change, and the two peaks converge to a predominant single peak. However, the ratio of van't Hoff enthalpy to calorimetric enthalpy is approximated to 2.0, indicating non-cooperativity in thermal unfolding.

Breaking the relay in deregulated cellular signal transduction as a rationale for chemoprevention with anti-inflammatory phytochemicals

Kundu, Joydeb Kumar,Surh, Young-Joon Elsevier 2005 Mutation research Vol.591 No.1-2

<P><B>Abstract</B></P><P>Center to the cancer biology is disrupted intracellular signaling network, which transmits improper signals resulting in abnormal cellular functioning. Therefore, modulation of inappropriate cell signaling cascades might be a rational approach in achieving chemoprevention. Inflammation has long been suspected to contribute to carcinogenesis. A new horizon in chemoprevention research is the recent discovery of molecular links between inflammation and cancer. Components of the cell signaling network, especially those converge on redox-sensitive transcription factor nuclear factor-κB involved in mediating inflammatory response, have been implicated in carcinogenesis. Intracellular signaling through another redox-sensitive transcription factor AP-1 and that transmitted via a more recently identified oncoprotein β-catenin are also considered to be crucial for inflammation-associated cancer. Epidemiological and experimental studies have revealed that a wide variety of phytochemicals present in our daily diet are potential chemopreventive agents that can alter or correct undesired cellular functions caused by abnormal pro-inflammatory signal transmission. Modulation of cellular signaling involved in chronic inflammatory response by anti-inflammatory phytochemicals may comprise a rational and pragmatic strategy in molecular target-based chemoprevention.</P>

Template mediated protein self-assembly as a valuable tool in regenerative therapy

Kundu, B,Eltohamy, M,Yadavalli, VK,Reis, RL,Kim, HW Institute of Physics Publishing Ltd 2018 Biomedical Materials Vol.13 No.4