Photo-induced DNA scission by Cu(ii)-meso-tetrakis(n-N-methylpyridiniumyl)porphyrins (n = 2, 3, 4) and their binding modes to supercoiled DNA.

Chitrapriya, Nataraj,Park, Jongjin,Wang, Wei,Lee, Hyosun,Kim, Seog K RSC Publishing 2012 Metallomics Vol.4 No.5

<P>The photo-induced cleavage of pGEM-7zf-NIS super-coiled DNA by Cu(ii)-meso-tetrakis(n-N-methylpyridiniumyl)porphyrins (n = 2, 3, 4 referred to as o-, m- and p-CuTMPyP, respectively) and their binding mode were investigated in this study. m-CuTMPyP was most efficient in cleavage than o- and p-CuTMPyP isomers. Cleavage was suppressed by N(2) bubbling, suggesting that the cleavage occurred by an oxidative cleavage mechanism. Sodium azide, an (1)O(2) quencher, and DMSO, a hydroxyl radical scavenger, inhibited cleavage, indicating that hydroxyl radicals and singlet oxygen were likely reactive species responsible for the cleavage. Reduced linear dichroism spectroscopy showed angles of o-CuTMPyP's electric transition moments, in which the periphery pyridinium ring was prevented from free rotation, of 59 and 61 with respect to the local DNA helix axis. The spectra of m- and p-CuTMPyP complexed with pGEM-7zf-NIS DNA were characterized by large signals in the Soret band, coincident with those of known intercalated porphyrins.</P>

Sequence Dependent Binding Modes of the ΔΔ- and ΛΛ-binuclear Ru(II) Complexes to poly[d(G-C)₂] and poly[d(A-T)₂]

Chitrapriya, Nataraj,Kim, Raeyeong,Jang, Yoon Jung,Cho, Dae Won,Han, Sung Wook,Kim, Seog K. Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.7

The binding properties and sequence selectivities of ${\Delta}{\Delta}$- and ${\Lambda}{\Lambda}-[{\mu}-Ru_2(phen)_4(bip)]^{4+}$ (bip = 4,4'-biphenylene (imidazo [4,4-f][1,10]phenanthroline) complexes with $poly[d(A-T)_2]$ and $poly[d(G-C)_2]$ were investigated using conventional spectroscopic methods. When bound to $poly[d(A-T)_2]$, a large positive circular dichroism (CD) spectrum was induced in absorption region of the bridging moiety for both the ${\Delta}{\Delta}$- and ${\Lambda}{\Lambda}-[{\mu}-Ru_2(phen)_4(bip)]^{4+}$ complexes, which suggested that the bridging moiety sits in the minor groove of the polynucleotide. As luminescence intensity increased, decay times became longer and complexes were well-protected from the negatively charged iodide quencher compared to that in the absence of $poly[d(A-T)_2]$. These luminescence measurements indicated that Ru(II) enantiomers were in a less polar environment compared to that in water and supported by minor groove binding. An angle of $45^{\circ}$ between the molecular plane of the bridging moiety of the ${\Delta}{\Delta}-[{\mu}-Ru_2(phen)_4(bip)]^{4+}$ complex and the local DNA helix axis calculated from reduced linear dichroism ($LD^r$) spectrum further supported the minor groove binding mode. In the case of ${\Lambda}{\Lambda}-[{\mu}-Ru_2(phen)_4(bip)]^{4+}$ complex, this angle was $55^{\circ}$, suggesting a tilt of DNA stem near the binding site and bridging moiety sit in the minor groove of the $poly[d(A-T)_2]$. In contrast, neither ${\Delta}{\Delta}$-nor ${\Lambda}{\Lambda}-[{\mu}-Ru_2(phen)_4(bip)]^{4+}$ complex produced significant CD or $LD^r$ signal in the absorption region of the bridging moiety. Luminescence measurements revealed that both the ${\Delta}{\Delta}$- and ${\Lambda}{\Lambda}-[{\mu}-Ru_2(phen)_4(bip)]^{4+}$ complexes were partially accessible to the $I^-$ quencher. Furthermore, decay times became shorter when bis-Ru(II) complexes bound to $poly[d(G-C)_2]$. These observations suggest that both the ${\Delta}{\Delta}$- and ${\Lambda}{\Lambda}-[{\mu}-Ru_2(phen)_4(bip)]^{4+}$ complexes bind at the surface of $poly[d(G-C)_2]$, probably electrostatically to phosphate group. The results indicate that ${\Delta}{\Delta}$- and ${\Lambda}{\Lambda}-[{\mu}-Ru_2(phen)_4(bip)]^{4+}$ are able to discriminate between AT and GC base pairs.

Sequence Dependent Binding Modes of the ΔΔ- and ΛΛ-binuclear Ru(II) Complexes to poly[d(G-C)2] and poly[d(A-T)2]

Nataraj Chitrapriya,Raeyeong Kim,장윤정,조대원,한성욱,김석규 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.7

The binding properties and sequence selectivities of ΔΔ- and ΛΛ-[μ-Ru2(phen)4(bip)]4+ (bip = 4,4'-biphenylene (imidazo [4,4-f][1,10]phenanthroline) complexes with poly[d(A-T)2] and poly[d(G-C)2] were investigated using conventional spectroscopic methods. When bound to poly[d(A-T)2], a large positive circular dichroism (CD) spectrum was induced in absorption region of the bridging moiety for both the ΔΔ- and ΛΛ-[μ- Ru2(phen)4(bip)]4+ complexes, which suggested that the bridging moiety sits in the minor groove of the polynucleotide. As luminescence intensity increased, decay times became longer and complexes were wellprotected from the negatively charged iodide quencher compared to that in the absence of poly[d(A-T)2]. These luminescence measurements indicated that Ru(II) enantiomers were in a less polar environment compared to that in water and supported by minor groove binding. An angle of 45° between the molecular plane of the bridging moiety of the ΔΔ-[μ-Ru2(phen)4(bip)]4+ complex and the local DNA helix axis calculated from reduced linear dichroism (LDr) spectrum further supported the minor groove binding mode. In the case of ΛΛ- [μ-Ru2(phen)4(bip)]4+ complex, this angle was 55°, suggesting a tilt of DNA stem near the binding site and bridging moiety sit in the minor groove of the poly[d(A-T)2]. In contrast, neither ΔΔ- nor ΛΛ-[μ-Ru2(phen)4- (bip)]4+ complex produced significant CD or LDr signal in the absorption region of the bridging moiety. Luminescence measurements revealed that both the ΔΔ- and ΛΛ-[μ-Ru2(phen)4(bip)]4+ complexes were partially accessible to the I− quencher. Furthermore, decay times became shorter when bis-Ru(II) complexes bound to poly[d(G-C)2]. These observations suggest that both the ΔΔ- and ΛΛ-[μ-Ru2(phen)4(bip)]4+ complexes bind at the surface of poly[d(G-C)2], probably electrostatically to phosphate group. The results indicate that ΔΔ- and ΛΛ-[μ-Ru2(phen)4(bip)]4+ are able to discriminate between AT and GC base pairs.

Behavior of the Guanine Base in G-quadruplexes Probed by the Fluorescent Guanine Analog, 6-Methyl Isoxanthopterin

한지훈,Nataraj Chitrapriya,이현석,이영애,김석규,정맹준 대한화학회 2017 Bulletin of the Korean Chemical Society Vol.38 No.2

In this study, circular dichroism (CD) spectrum and fluorescence techniques were used to examine the dynamic properties and microenvironment of the guanine base (G) at the central loop and at the middle of the G-stem of the G-quadruplex formed from the G3T2G3TGTG3T2G3 sequence (G-quadruplex 1), in which the G base at the 10th and 13th position were replaced with a fluorescent G analog, 6-methyl isoxanthopterin (6MI) (G-quadruplex 2 and 3, respectively). For all G-quadruplexes, the CD spectrum revealed a positive band at 263 nm and a shoulder at 298 nm, and the thermal melting profiles were the sum of at least two sigmoidal curves. These observations indicated the presence of two conformers in the G-quadruplex. The fluorescence intensity of G-quadruplex 2 was greater than 3, as expected from the extent of stacking interaction, which is larger in the G(6MI)G sequence than the T(6MI)T sequence. The efficiency of fluorescence quenching by the polar acrylamide quencher and negatively charged I− quencher were larger for G-quadruplex 3, suggesting that 6MI in the G(6MI)G stem is exposed more to the aqueous environment compared to that in the T(6MI)T central loop. In the latter case, 6MI may direct to the center of the top G-quartet layer. The possibility of hydrogen bond formation between the carbonyl group of 6MI and the acrylamide of the G-quadruplex 3 was proposed.

Direction of Intercalation of a bis-Ru(II) Complex to DNA Probed by a Minor Groove Binding Molecule 4',6-Diamidino-2-phenylindole

장윤정,Raeyeong Kim,Nataraj Chitrapriya,한성욱,김석규,배인호 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.10

Direction of intercalation to DNA of the planar dipyrido[3,2-a:2',3'-c]phenazine ligands (dppz) of a bis-Ru(II) complex namely, [Ru(1,10-phenanthroline)2dipyrido[3,2-a:2',3'-c]phenazine]2+ linkered by a 1,3-bis(4- pyridyl)propane, was investigated by probing the behavior of 4',6-diamidino-2-phenylindole (DAPI) that bound deep in the minor groove. Bis-intercalation of DPPZ resulted in a little blue shift and hyperchromism in DAPI absorption band, and a large decrease in DAPI fluorescence intensity which accompined by an increase in the dppz emission intensity. Diminishing the intenisty of the positive induced circular dichroism (CD) and linear dichroism (LD) were also observed. These spectral changes indicated that insertion of dppz ligand caused the change of the binding mode of DAPI, which probably moved to the exterior of DNA from the minor groove and interacted with the phospghate groups of DNA by electrostatic interaction. At the surface of DNA, DAPI binds at the phosphate groups of DNA by electrostatic attraction. Consequently, this observation indicated that the dppz ligand intercalated from the minor groove.

Facile construction of bioreducible crosslinked polypeptide micelles for enhanced cancer combination therapy

Ruttala, Hima Bindu,Chitrapriya, Natarajan,Kaliraj, Kaliappan,Ramasamy, Thiruganesh,Shin, Woo Hyun,Jeong, Jee-Heon,Kim, Jae Ryong,Ku, Sae Kwang,Choi, Han-Gon,Yong, Chul Soon,Kim, Jong Oh Elsevier Science B.V. Amsterdam 2017 ACTA BIOMATERIALIA Vol. No.

<P><B>Abstract</B></P> <P>In this study, we developed pH and redox-responsive crosslinked polypeptide-based combination micelles for enhanced chemotherapeutic efficacy and minimized side effects. The stability and drug release properties of the polypeptide micelles were efficiency balanced by the corona-crosslinking of the triblock copolymer, poly(ethylene glycol)-<I>b</I>-poly(aspartic acid)-<I>b</I>-poly(tyrosine) (PEG-<I>b</I>-pAsp-<I>b</I>-pTyr) with coordinated redox and pH dual-sensitivity by introducing disulfide crosslinkages. Because of the crosslinking of the middle shell of the triblock polypeptide micelles, their robust structure was maintained in strong destabilization conditions and exhibited excellent stability. GSH concentrations were significantly higher in tumor tissue than in normal tissue, which formed the basis for our design. Drug release was elevated under redox and low acidic conditions. Furthermore, crosslinked micelles showed a superior anticancer effect compared to that of non-crosslinked micelles. Incorporation of docetaxel (DTX) and lonidamine (LND) in crosslinked polypeptide micelles increased the intracellular reactive oxygen species (ROS) level and oxidative stress and caused damage to intracellular components that resulted in greater apoptosis of cancer cells than when DTX or LND was used alone. The combination of DTX and LND in crosslinked micelles exhibited efficacious inhibition of tumor growth with an excellent safety profile compared to that reported for drug cocktail combinations and non-crosslinked micelles. Overall, redox/pH-responsive polypeptide micelles could be an interesting platform for efficient chemotherapy.</P> <P><B>Statement of Significance</B></P> <P>We have synthesized a biodegradable polypeptide block copolymer to construct a facile pH and redox-responsive polymeric micelle asan advanced therapeutic system for cancer therapy. We have designed a corona-crosslinked triblock copolymer (poly (ethylene glycol)-<I>b</I>-poly(aspartic acid)-<I>b</I>-poly(tyrosine) (PEG-<I>b</I>-pAsp-<I>b</I>-pTyr)) micelles co-loaded with docetaxel and lonidamine (cl-M/DL). The corona of triblock polymer was crosslinked to maintain its structural integrity in the physiological environment. The mitochondrial targeting LND is expected to generate ROS, oxidative stress and thereby synergize the chemotherapeutic efficacy of DTX in killing cancer cells. Consistently, cl-M/DL exhibited excellent antitumor efficacy in xenograft tumor model with remarkable tumor regression. Overall, we demonstrated the construction of bioreducible nanosystem for the effective synergistic delivery of DTX/LND in tumor tissues towards cancer treatment.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Ruthenium(II)/(III) complexes of 4-hydroxy-pyridine-2,6-dicarboxylic acid with PPh₃/AsPh₃ as co-ligand: Impact of oxidation state and co-ligands on anticancer activity <i>in vitro</i>

Kamatchi, Thangavel Sathiya,Chitrapriya, Nataraj,Lee, Hyosun,Fronczek, Chris F.,Fronczek, Frank R.,Natarajan, Karuppannan The Royal Society of Chemistry 2012 Dalton transactions Vol.41 No.7

<P>With the aim to develop more efficient, less toxic, target specific metal drugs and evaluate their anticancer properties in terms of oxidation state and co-ligand sphere, a sequence of Ru<SUP>II</SUP>, Ru<SUP>III</SUP> complexes bearing 4-hydroxy-pyridine-2,6-dicarboxylic acid and PPh<SUB>3</SUB>/AsPh<SUB>3</SUB> were synthesized and structurally characterized. Biological studies such as DNA binding, antioxidant assays and cytotoxic activity were carried out and their anticancer activities were evaluated. Interactions of the complexes with calf thymus DNA revealed that the triphenylphosphine complexes could bind more strongly than the triphenylarsine complexes. The free radical scavenging ability, assessed by a series of <I>in vitro</I> antioxidant assays involving DPPH radical, hydroxyl radical, nitric oxide radical, superoxide anion radical, hydrogen peroxide and metal chelating assay, showed that the Ru<SUP>III</SUP> complexes possess excellent radical scavenging properties compared to those of Ru<SUP>II</SUP>. Cytotoxicity studies using three cancer lines <I>viz</I> HeLa, HepG2, HEp-2 and a normal cell line NIH 3T3 showed that Ru<SUP>II</SUP> complexes exhibited substantial cytotoxic specificity towards cancer cells. Furthermore, the Ru<SUP>II</SUP> complexes were found to be superior to Ru<SUP>III</SUP> complexes in inhibiting the growth of cancer cells.</P> <P>Graphic Abstract</P><P>We investigate the effects of oxidation states of ruthenium and the size of the ligands present in the complexes on DNA binding, antioxidant activity and cytotoxicity. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1dt11273b'> </P>

Engineering of cell microenvironment-responsive polypeptide nanovehicle co-encapsulating a synergistic combination of small molecules for effective chemotherapy in solid tumors

Ramasamy, Thiruganesh,Ruttala, Hima Bindu,Chitrapriya, Nataraj,Poudal, Bijay Kumar,Choi, Ju Yeon,Kim, Ssang Tae,Youn, Yu Seok,Ku, Sae Kwang,Choi, Han-Gon,Yong, Chul Soon,Kim, Jong Oh Elsevier 2017 ACTA BIOMATERIALIA Vol.48 No.-

<P><B>Abstract</B></P> <P>In this study, we report a facile method to construct a bioactive (poly(phenylalanine)-<I>b</I>-poly(<SMALL>L</SMALL>-histidine)-<I>b</I>-poly(ethylene glycol) polypeptide nanoconstruct to co-load doxorubicin (DOX) and quercetin (QUR) (DQ-NV). The smart pH-sensitive nanovehicle was fabricated with precisely tailored drug-to-carrier ratio that resulted in accelerated, sequential drug release. As a result of ratiometric loading, QUR could significantly enhance the cytotoxic potential of DOX, induced marked cell apoptosis; change cell cycle patterns, inhibit the migratory capacity of sensitive and resistant cancer cells. In particular, pro-oxidant QUR from DQ-NV remarkably reduced the GSH/GSSG ratio, indicating high oxidative stress and damage to cellular components. DQ-NV induced tumor shrinkage more effectively than the single drugs in mice carrying subcutaneous SCC-7 xenografts. DQ-NV consistently induced high expression of caspase-3 and PARP and low expression of Ki67 and CD31 immunomarkers. In summary, we demonstrate the development of a robust polypeptide-based intracellular nanovehicle for synergistic delivery of DOX/QUR in cancer chemotherapy.</P> <P><B>Statement of Significance</B></P> <P>In this study, we report a facile method to construct bioactive and biodegradable polypeptide nanovehicles as an advanced platform technology for application in cancer therapy. We designed a robust (poly(phenylalanine)-<I>b</I>-poly(<SMALL>L</SMALL>-histidine)-<I>b</I>-poly(ethylene glycol) nanoconstruct to co-load doxorubicin (DOX) and quercetin (QUR) (DQ-NV). The conformational changes of the histidine block at tumor pH resulted in accelerated, sequential drug release. QUR could significantly enhance the cytotoxic potential of DOX, induce marked cell apoptosis, change cell cycle patterns, and inhibit the migratory capacity of sensitive and resistant cancer cells. DQ-NV induced tumor shrinkage more effectively than the single drugs and the 2-drug cocktail in tumor xenografts<I>.</I> In summary, we demonstrate the development of an intracellular nanovehicle for synergistic delivery of DOX/QUR in cancer chemotherapy.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Direction of Intercalation of a bis-Ru(II) Complex to DNA Probed by a Minor Groove Binding Molecule 4',6-Diamidino-2-phenylindole

Jang, Yoon Jung,Kim, Raeyeong,Chitrapriya, Nataraj,Han, Sung Wook,Kim, Seog K.,Bae, Inho Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.10

Direction of intercalation to DNA of the planar dipyrido[3,2-a:2',3'-c]phenazine ligands (dppz) of a bis-Ru(II) complex namely, $[Ru(1,10-phenanthroline)_2dipyrido[3,2-a:2^{\prime},3^{\prime}-c]phenazine]^{2+}$ linkered by a 1,3-bis(4-pyridyl)propane, was investigated by probing the behavior of 4',6-diamidino-2-phenylindole (DAPI) that bound deep in the minor groove. Bis-intercalation of DPPZ resulted in a little blue shift and hyperchromism in DAPI absorption band, and a large decrease in DAPI fluorescence intensity which accompined by an increase in the dppz emission intensity. Diminishing the intenisty of the positive induced circular dichroism (CD) and linear dichroism (LD) were also observed. These spectral changes indicated that insertion of dppz ligand caused the change of the binding mode of DAPI, which probably moved to the exterior of DNA from the minor groove and interacted with the phospghate groups of DNA by electrostatic interaction. At the surface of DNA, DAPI binds at the phosphate groups of DNA by electrostatic attraction. Consequently, this observation indicated that the dppz ligand intercalated from the minor groove.

Effect of Number and Location of Amine Groups on the Thermodynamic Parameters on the Acridine Derivatives to DNA

Kwon, Ji Hye,Park, Hee-Jin,Chitrapriya, Nataraj,Han, Sung Wook,Lee, Gil Jun,Lee, Dong Jin,Cho, Tae-Sub Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.3

The thermodynamic parameters for the intercalative interaction of structurally related well known intercalators, 9-aminoacridine (9AA) and proflavine (PF) were determined by means of fluorescence quenching study. The fluorescence intensity of 9AA decreased upon intercalation to DNA, poly[$d(A-T)_2$] and poly[$d(G-C)_2$]. A van't Hoff plot was constructed from the temperature-dependence of slope of the ratio of the fluorophore in the absence and presence of a quencher molecule with respect to the quencher concentration, which is known as a Stern-Volmer plot. Consequently, the thermodynamic parameters, enthalpy and entropy change, for complex formation was calculated from the slope and y-intercept of the van't Hoff plot. The detailed thermodynamic profile has been elucidated the exothermic nature of complex formation. The complex formation of 9AA with DNA, poly[$d(A-T)_2$] and poly[$d(G-C)_2$] was energetically favorable with a similar negative Gibb's free energy. On the other hand, the entropy change appeared to be unfavorable for 9AA-poly[$d(G-C)_2$] complex formation, which was in contrast to that observed with native DNA and poly[$d(A-T)_2$] cases. The equilibrium constant for the intercalation of PF to poly[$d(G-C)_2$] was larger than that to DNA, and was the largest among sets tested despite the most unfavorable entropy change, which was compensated for by the largest favorable enthalpy. The favorable hydrogen bond contribution to the formation of the complexes was revealed from the analyzed thermodynamic data.