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>

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>

Evaluation of hepatoprotective activity of ethanol extract of Coccinia grandis (L.) Voigt. leaves on experimental rats by acute and chronic models

Kundu, Mintu,Mazumder, Rupa,Kushwaha, M.D. 경희한의학연구센터 2012 Oriental Pharmacy and Experimental Medicine Vol.12 No.2

Coccinia grandis Linn. (Cucurbitaceae) is a climbing perennial branched herb, distributed throughout India. Other plants under the same family have been reported for their hepatoprotective activity. The aim of this work was to study the hepatoprotective effect of crude ethanolic extract from the leaves of C. grandis against liver damage induced by Paracetamol and $CCl_4$ in rats. Administration of Paracetamol (750 mg/kg/day) and $CCl_4$ (3 ml/kg/day) showed a marked increase in SGOT, SGPT, ALP, bilirubin (total, direct), total proteins, globulin, cholesterol and decrease in albumin in comparison with the normal control group. The effect of ethanol extract of C. grandis at 150 mg/kg and 300 mg/kg doses reduced the serum activities caused by Paracetamol and $CCl_4$, which were observed to be statistically significant when compared with that of the control group. The activity exhibited/inhibited by the plant extract was found to be comparable to that of the standard hepatoprotective drug, Silymarin. Silymarin provided a better inhibition or exhibition of the biochemical parameters induced by paracetamol and carbon tetrachloride in rats. The activity may be due to the presence of either alkaloids or triterpenoids or reducing sugars or their combinations, as obtained from the preliminary phytochemical screening of the leaves of the plant. The extract showed no signs of acute toxicity up to a dose level of $3.2gkg^{-1}$ in rats by oral route. Thus, it could be concluded that ethanolic extract of C. grandis leaves possessed significant hepatoprotective activity.

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>

Fluorescent carbon nano-materials from coal-based precursors: unveiling structure–function relationship between coal and nano-materials

Kundu Niloy,Sadhukhan Dhrubajyoti,Sarkar Supriya 한국탄소학회 2022 Carbon Letters Vol.32 No.3

Fluorescent carbon nano-materials with quantum confinement and edge effects have recently piqued attention in a variety of applications, including biological imaging, drug delivery, optoelectronics and sensing. These nano-materials can be synthesized from a variety of carbon-based precursors using both top-down and bottom-up methods. Coal and its derivatives typically include a vast crystalline network and condensed aromatic ring cluster, which can be easily exfoliated by chemical, electrochemical, or physical processes to produce nano-materials. As a result, they are regarded as a low-cost, abundant and efficient carbon source for the fabrication of high-yield nano-materials. Nano-materials synthesized from coal-based precursors have outstanding fluorescence, photostability, biocompatibility and low toxicity, among other properties. Their properties in optical sensors, LED devices, bio-imaging, and photo and electro-catalyst applications have already been investigated. In this review, we have highlighted current developments in the synthesis, structural properties and fluorescence properties of nano-materials synthesized from coal-based precursors.

The Promise of Dried Fruits in Cancer Chemoprevention

Kundu, Joydeb Kumar,Chun, Kyung-Soo Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.8

Chemoprevention is an attempt to use nontoxic natural and synthetic substances or their mixtures to intervene the relatively early stages of carcinogenesis, before invasive characteristics are manifested. The consumption of fruits is well known to reduce the risk of human cancers. Although most fruits are available only on a seasonal basis, recent advances in food processing technologies have made it possible to extend the shelf life of fruits and fruit-products. Fruits can be preserved by applying different drying processes to reduce the moisture content. Different varieties of dried fruits are now sold in supermarkets, thereby making them readily accessible to consumers. Since oxidative stress and chronic inflammation play important roles in cancer development, dried fruits with antioxidative and anti-inflammatory properties hold promise for cancer chemoprevention. The antioxidant, anti-inflammatory and chemopreventive activities of dried fruits are largely attributed to their polyphenols and vitamins. Dried fruits contain adequate amounts of bioactive principles, such as anthocyanins, acetogenins, catechins, coumarins, phenolic acids, terpenes, xanthones, and others. Since numerous health beneficial phytochemicals in fruits are conserved even after processing, regular intake of dried fruits can help prevent cancer. This review addresses the chemopreventive potential of representative dried fruits and their active constituents.

Studying Water Hydrogen-Bonding Network near the Lipid Multibilayer with Multiple IR Probes

Kundu, Achintya,Verma, Pramod Kumar,Ha, Jeong-Hyon,Cho, Minhaeng American Chemical Society 2017 The Journal of physical chemistry A Vol.121 No.7

<P>A critical difference between living and nonliving is the existence of cell membranes, and hydration of membrane surface is a prerequisite for structural stability and various functions such as absorption/desorption of drugs, proteins, and ions. Therefore, a molecular level understanding of water structure and dynamics near the membrane is important to perceive the role of water in such a biologically relevant environment. In our recent paper [J. Phys. Chem. Lett. 2016, 7, 741] on the IR pump probe study of the OD stretch mode of HDO near lipid multibilayers, we have observed two different vibrational lifetime components of OD stretch mode in the phospholipid multibilayer systems. The faster component (0.6 ps) is associated with OD groups interacting with the phosphate moiety of the lipid, while the slower component (1.9 ps) is due to choline-associated water molecules that are close to bulklike water. Here, we additionally use hydrazoic acid (HN3) as another IR probe of which frequency is highly sensitive to its local H-bonding water density. Interestingly, we found that the vibrational lifetime of the asymmetric azido stretch mode of HN3 in the lipid multibilayer system is similar to that in neat water, whereas its orientational relaxation is a bit slower than that in bulk water. This indicates that due to the tight packing of lipid molecules, particularly the head parts, in the gel phase, HN3 molecules mostly stay near the choline group of lipid and interact with water molecules in the vicinity of choline groups. This suggests that membrane surface-adsorbed molecules such as hydrophilic drug molecules may interact with choline-associated water molecules, when the membrane is in the gel phase, instead of phosphate-associated water molecules.</P>

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>

Unusual fluorescent photoswitching of imidazole derivatives: the role of molecular conformation and twist angle controlled organic solid state fluorescence

Kundu, Anu,Karthikeyan, Subramanian,Sagara, Yoshimitsu,Moon, Dohyun,Anthony, Savarimuthu Philip The Royal Society of Chemistry 2018 Physical Chemistry Chemical Physics Vol.20 No.43

<P>Molecular photoswitching, light induced reversible color/fluorescence modulation, has mostly been realized in organic molecules <I>via E</I>/<I>Z</I> isomerization of azobenzenes and stilbenes and ring opening/closing reactions of spiropyrans and diarylethenes. We report here new fluorescent molecular photoswitches based on triphenylamine (TPA)-imidazole derivatives, <I>N</I>-phenyl-<I>N</I>-(4-(1,4,5-triphenyl-1<I>H</I>-imidazol-2-yl)phenyl)benzenamine (NTPB) and <I>N</I>-phenyl-<I>N</I>-(4-(1-phenyl-1<I>H</I>-phenanthro[9,10-<I>d</I>]imidazol-2-yl)phenyl)benzenamine (NPPB), that exhibited light induced reversible fluorescence switching <I>via</I> conformational change from a twisted molecular structure to more planar. NTPB and NPPB in CHCl3 showed red shift of absorption and fluorescence upon UV light irradiation whereas white light exposure reversed both absorption as well as fluorescence. The role of the TPA-imidazole twisted molecular structure in photoswitching was established based on structure property, computational and photophysical studies. The isobestic point observed in time dependent fluorescence change under UV light irradiation clearly demonstrated the presence of two different conformational isomers. Interestingly, polymorphism and torsion angle (<I>τ</I>) dependent fluorescence of NTPB and NPPB in the solid state also supported the role of the twisted molecular structure of TPA-imidazole in fluorescence switching/tuning. Interestingly, NTPB showed fluorescence photoswitching in the solid state also whereas rigid phenanthrene based NPPB did not show fluorescence photoswitching. Thus the present studies provide structural insight for designing a new type of fluorescent organic molecular photoswitches based on conformational modulation that could be of potential interest in optoelectronic devices.</P>