Affinity For Poly Research Articles

Design of peptides with strong binding affinity to poly(methyl methacrylate) resin by use of molecular simulation-based materials informatics

Peptides with strong binding affinities for poly(methyl methacrylate) (PMMA) resin were designed by use of materials informatics technology based on molecular dynamics simulation for the purpose of covering the resin surface with adhesive peptides, which were expected to result in eco-friendly and biocompatible biomaterials. From the results of binding affinity obtained with this molecular simulation, it was confirmed that experimental values could be predicted with errors <10%. By analyzing the simulation data with the response-surface method, we found that three peptides (RWWRPWW, EWWRPWR, and RWWRPWR), which consist of arginine (R), tryptophan (W), and proline (P), have strong binding affinity to the PMMA resin. These amino acids were effective because arginine and tryptophan have strong binding affinities for methoxycarbonyl groups and methyl groups, which are the main constituents of the PMMA resin, and proline stabilizes the flat zigzag structures of the peptides in water. The strong binding affinities of the three peptides were confirmed by experiments (surface plasmon resonance methods).

A glycine-rich protein MoGrp1 functions as a novel splicing factor to regulate fungal virulence and growth in Magnaporthe oryzae

Glycine-rich proteins (GRPs) have diverse amino acid sequences and are involved in a variety of biological processes. The role of GRPs in plant pathogenic fungi has not been reported. In this study, we identified and functionally characterized a novel gene named MoGRP1 in Magnaporthe oryzae, which encodes a protein that has an N-terminal RNA recognition motif (RRM) and a C-terminal glycine-rich domain with four Arg-Gly-Gly (RGG) repeats. Deletion of MoGRP1 resulted in dramatic reductions in fungal virulence, mycelial growth, and conidiation. The ΔMogrp1 mutants were also defective in cell wall integrity and in their responses to different stresses. MoGrp1 was localized to the nucleus and was co-immunoprecipitated with several components of the spliceosome, including subunits of the U1 snRNP and U2 snRNP complexes. Moreover, MoGrp1 exhibited binding affinity for poly(U). Importantly, MoGrp1 was responsible for the normal splicing of genes involved in infection-related morphogenesis. Domain deletion assays showed that both the RRM domain and its two adjacent RGG repeats were essential to the full function of MoGrp1. Notably, the nine amino acids between the first and the second RGG repeats were indispensable for nuclear localization and for the biological functions of MoGrp1. Taken together, our data suggest that MoGrp1 functions as a novel splicing factor with poly(U) binding activity to regulate fungal virulence, development, and stress responses in the rice blast fungus.

Affinity‐tuned peroxidase‐like activity of hydrogel‐supported Fe3O4 nanozyme through alteration of crosslinking concentration

ABSTRACTIn this work, we evaluated the effect of crosslinking concentration on the affinity of poly (2‐acrylamido‐2‐methyl‐1‐propansulfonic acid) (PAMPS) hydrogel‐supported Fe3O4 nanozyme towards substrates (tetramethylbenzidine (TMB) and H2O2). The peroxidase‐like catalytic activity of PAMPS/Fe3O4 nanozyme was discussed with respect to crosslinking concentration of PAMPS hydrogel for the oxidation of TMB in the presence of H2O2 at room temperature. High catalytic activity was achieved due to good dispersion of Fe3O4 nanozyme in the hydrogel network and strong affinity of PAMPS hydrogel‐supported Fe3O4 nanozyme towards substrates. The affinity between the hydrogel‐supported Fe3O4 nanozyme and substrates can be improved by regulating the crosslinking concentration of PAMPS hydrogel without other trenchant experimental conditions. In addition, the result indicated that H2O2 can be detected even at a concentration as low as 1.5 × 10−6 mol L−1 with a linear detection range of 1.5–9.8 × 10−6 mol L−1. Such investigations not only showed a new approach to improve the affinity and peroxidase‐like activity of Fe3O4 nanozyme, but also verified its potential application in bio‐detection and environmental chemistry. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43065.

DNA and RNA Noncovalent Interaction of Platinum(II) Polypyridine Complexes

A comparative investigation of the noncovalent interaction of the platinum(II) polypyridine complexes [Pt(dipy)(n-Rpy)2]2+ and [Pt(4,4'-Me2dipy)(2-Rpy)2]2+ (dipy = 2,2'-dipyridine; Me = CH3; n = 2-4; R = H or CH3) with double-helical DNA (calf thymus) and RNA [poly(A).poly(U)] has been conducted. With the exception of [Pt(dipy)(2-Mepy)2]2+, all of the complexes interact strongly, by intercalation, with both nucleic acids giving rise to large changes in the electronic spectra and induced circular dichroism signals; in addition, viscosity experiments on rodlike DNA and RNA show that both biopolymers elongate upon interaction with the complexes. The binding constant values, KB, determined at 25 degrees C, indicate that, at 0.101 M ionic strength, the affinity for poly(A).poly(U) is strongly dependent on the complexes nature, while for DNA it is leveled off. [Pt(dipy)(2-Mepy)2]2+ binds to DNA but does not interact appreciably with poly(A).poly(U).

DNA Binding Thermodynamics and Sequence Specificity of Chiral Piperazinecarbonyloxyalkyl Derivatives of Anthracene and Pyrene

In this paper we report the DNA binding proper ties of piperazinecarbonyloxy-2-propyl derivatives of anthracene (2), pyrene (3), and phenylanthracene (4). An intercalative binding mode is found for 2 and 3, while the phenyl group of 4 prevents intercalation and leads to external binding. Preferential binding of the (S)-enantiomers is found for both anthracene 2 and pyrene 3. However, the enantiomeric preference is small, with K-(R)/K-(S) being around 0.5 for both the anthracene and the pyrene compounds. This is interpreted in terms of orientation polarity in the binding, by which any intrinsic enantioselectivity is canceled by averaging of opposite binding orientations. The affinities for poly(dA-dT)(2) (AT) are 10(4) M-1 for anthracene derivative 2, and 5 x 10(5) M-1 for pyrene derivative 2. The affinities for poly(dG-dC)(2) (GC) are I order of magnitude lower than those for AT. This is explained by steric interference of the piperazinium tail with the exocyclic amino groups of guanine in the minor groove of GC, leading to a more shallow intercalation in GC than in AT, as also indicated by significantly less negative reduced linear dichroism of the intercalator absorption bands in the GC complexes. This behavior is consistent with that observed for the previously studied achiral analogues.(1) Binding thermodynamics support the difference in binding mode between AT and GC. The binding enthalpy of the AT complexes is significantly more negative than that of the corresponding GC complexes. This indicates a larger overlap of intercalating moiety and nucleobases in the AT complexes, consistent with the linear dichroism results.

High Oxygen-Binding Affinity of Poly(4-Vinylimidazole-co-octylmethacrylate)-Cobaltporphyrin Complex: Effect of Hydrogen-Bond at the Imidazole Residue

The oxygen-binding affinity of the cobalt-picketfence-porphyrin (CoP) ligated with imidazole was enhanced in the presence of an additive which forms a hydrogen-bond with the ligated imidazole. The CoP complex with poly(4(5)-vinylimidazole-co-octylmethacrylate) rapidly and reversibly bound oxygen and showed very high oxygen-binding affinity: The oxygen transport in the CoP-polymer membrane was efficiently facilitated.

Heavy metal sequestration properties of a new amine-type chelating adsorbent

The performance of poly(CGMAPEI), an amine-type chelating adsorbent synthesized by graft polymerization, was evaluated in a simulated waste stream containing Cu2+ and Co2+ heavy metal ions and NaNO3 salt. Comparisons of metal adsorption curves of this adsorbent with a previously synthesized cellulose-PEI and commercially available chitosan-polyamine and amberlite resins were made. The poly(CGMAPEI) exhibited the highest capacity in the absence of NaNO3. At high concentrations of NaNO3, the affinities of all the amine-type adsorbents were found to be enhanced quite tremendously. The chelating adsorbent with the highest amine content (CS-03) showed the highest improvement in capacity. This phenomenon was not observed with the ion-exchanger (amberlite IRC 50) studied. Sodium ions showed negligible affinity for poly(CGMAPEI). Competition between Na+ with Cu2+ for adsorption sites in the adsorbent was absent. Regeneration experiments revealed some reduction in Cu2+ affinity of poly(CGMAPEI) after acid treatment. Difficulty in stripping Co2+ from poly(CGMAPEI) even by strong acid was also observed.

Biological activity of poly(maleic acid-alt-2-cyclohexyl-1,3-dioxepin-5-ene)

The polyanionic polymer poly(maleic acid-alt-2-cyclohexyl-1,3-dioxepin-5-ene), poly(MA-CDA), was developed as an immunomodulator. It was found that the cell affinity of poly(MA-CDA) could be significantly enhanced by hydrophobic chemical modification. This paper deals with the biological activities of poly(MA-CDA) and hydrophobically modified poly(MA-CDA), including immunostimulating activity, antitumour activity and antiviral activity. © 1998 SCI.

Heavy metal sequestration properties of a new amine-type chelating adsorbent

The performance of poly(CGMAPEI), an amine-type chelating adsorbent synthesized by graft polymerization, was evaluated in a simulated waste stream containing Cu2+ and Co2+ heavy metal ions and NaNO3 salt. Comparisons of metal adsorption curves of this adsorbent with a previously synthesized cellulose-PEI and commercially available chitosan-polyamine and amberlite resins were made. The poly(CGMAPEI) exhibited the highest capacity in the absence of NaNO3. At high concentrations of NaNO3, the affinities of all the amine-type adsorbents were found to be enhanced quite tremendously. The chelating adsorbent with the highest amine content (CS-03) showed the highest improvement in capacity. This phenomenon was not observed with the ion-exchanger (amberlite IRC 50) studied. Sodium ions showed negligible affinity for poly(CGMAPEI). Competition between Na+ with Cu2+ for adsorption sites in the adsorbent was absent. Regeneration experiments revealed some reduction in Cu2+ affinity of poly(CGMAPEI) after acid treatment. Difficulty in stripping Co2+ from poly(CGMAPEI) even by strong acid was also observed.

Single-Strand-Preferring RNases Degrade Double-Stranded RNAs by Destabilizing its Secondary Structure

To establish the mechanism of dsRNA degradation by mammalian single-stranded-preferring ribonucleases, and, in particular, the influence of their positively charged non-catalytic amino acid residies, we have studied the kinetic parameters of the depolimerization of single- and double-stranded polyribonucleotides such as poly(U), poly(U)·poly(A), poly(C) and poly(C)·poly(I) by the action of human seminal RNase, bovine seminal RNase and ox pancreas RNase A. While the activities of these RNases on poly(I)·poly(C) were definitely lower than those on poly(C), the activities of human seminal and bovine seminal RNases on poly(U)·poly(A) and poly(U) were of the same order of magnitude under physiological salt conditions. The ratio of the RNase A degrading activities towards poly(U) and poly(U)·poly(A) at I = 0.16 M is ten times higher than the corresponding ratios determined with bovine seminal and human seminal ribonucleases. The high activities of these two RNases towards poly(U)·poly(A) are discussed on the basis of their efficient destabilizing action on this double-helical nucleic acid due to their high affinity for poly(A). The destabilizing action of human seminal RNase and bovine seminal RNase on the poly(U)·poly(A) duplex is higher than that measurable with bovine RNase A because of the higher number of positive charges present on those enzyme molecules. This may therefore explain why human seminal and bovine seminal ribonucleases are more efficient than RNase A in the depolymerization of poly(U)·poly(A) at physiological ionic strength.

Affinity of poly(phenylcyanomethylenefluorene) and poly(dicyanomethylenefluorene) towards metallic cations. Uses of the new interfaces in electrocatalysis

Abstract Anodic oxidation of 2(9 H -fluoren-9-ylidene)malononitrile and 2(9 H -fluoren-9-ylidene)-2-phenylacetonitrile leads to polyfluorenylidene possessing an affinity towards some metallic cations leading to polymer-metal composites. The efficiency of these new interfaces is presented during the anodic oxidation of hydrazine, formaldehyde, methanol, glucose and sodium azide. For this last substrate, the detection limit with our new polymer-metal composite is lower than 5 × 10 −5 M.

Nucleic acid-binding properties of a bacterially expressed potato virus Y helper component-proteinase

The potyvirus helper component-proteinase (HC-Pro) is a multifunctional protein previously reported to have affinity for polyribonucleotides. To investigate further the ability of HC-Pro to bind nucleic acids, the potato virus Y (PVY) LYE84 isolate HC-Pro gene was amplified, cloned in an Escherichia coli expression vector and sequenced. HC-Pro was expressed as a fusion with the maltose-binding protein and purified by affinity chromatography. Electrophoretic mobility-shift assays demonstrated that HC-Pro acts as a sequence non-specific RNA-binding protein and suggest that more than one molecule of protein was bound per molecule of RNA. The HC-Pro RNA-binding activity was stable in 400 mm-NaCl and temperature sensitive. The recombinant protein preferentially bound ssRNA over DNA or dsRNA and showed little, if any, affinity for poly(A). The possible implications of the RNA-binding activity of HC-Pro in potyvirus replication and movement are discussed.

Proteins C1 and C2 of heterogeneous nuclear ribonucleoprotein complexes bind RNA in a highly cooperative fashion: support for their contiguous deposition on pre-mRNA during transcription.

Proteins C1 and C2 together comprise about one-third the protein mass of mammalian core 40S heterogeneous nuclear ribonucleoprotein particles (40S hnRNP) and exist as heterotetramers of (C1)3C2. On the basis of nonequilibrium binding studies, it has been suggested that the C proteins specifically bind oligo(U)- and poly(U)-rich sequences, and preferentially associate with uridine-rich regions near the 3' termini of many introns. We describe here a more quantitative characterization of the equilibrium binding properties of native and recombinant C protein to homoribopolymers using fluorescence spectroscopy. Like C protein from HeLa cells, the recombinant proteins spontaneously oligomerize to form tetramers with the same hydrodynamic properties as native protein. Near-stoichiometric binding titrations of the fluorescent homoribopolymer polyethenoadenosine (poly[r(epsilon A)]) with recombinant (C1)4 and (C2)4 homotetramers along with competition binding assays with poly(A) and poly(C) indicate that the binding site size (n) is between 150 and 230 nucleotides. This site size range is in close agreement with that previously determined for native C protein through hydrodynamic and ultrastructural studies (approximately 230 nucleotides). (C1)4 and (C2)4 bind poly(G) with intrinsic affinities (Ki) of 10(9) M-1, which are a hundredfold higher than their affinities for poly(U). In opposition to reports that C protein does not bind poly(A) and poly(C), we find that the C proteins bind these substrates with moderate Ki, but with high cooperativity (omega). The overall affinity (K omega) for the binding of both proteins to poly(A) and poly(C) is 10-fold higher (> 10(8) but < 10(9) M-1) than their affinities for poly(U). The highly cooperative binding of C protein to these substrates provides a mechanistic basis for the distribution of C protein along the length of nucleic acid substrates.

Affinity of guanosine derivatives for polycytidylate revisited.

Evidence is presented for complexation of guanosine 5'-monophosphate 2-methylimidazolide (2-MeImpG) with polycytidylate (poly(C)) at pH 8.0 and 23 degrees C in the presence of 1.0 M NaCl2 and 0.2 M MgCl2 in water. The association of 2-MeImpG with poly(C) was investigated using UV-vis spectroscopy as well as by monitoring the kinetics of the nucleophilic substitution reaction of the imidazole moiety by amines. The results of both methods are consistent with moderately strong poly(C) 2-MeImpG complexation and the spectrophotometric measurements allowed the construction of a binding isotherm with a concentration of 2-MeImpG equal to 5.55 +/- 0.15 mM at half occupancy. UV spectroscopy was employed to establish the binding of other guanosine derivatives on poly(C). These derivatives are guanosine 5'-monophosphate (5'GMP), guanosine 5'-monophosphate imidazolide (ImpG), and guanosine 5'-monophosphate morpholidate (morpG). Within experimental error these guanosine derivatives exhibit the same affinity for poly(C) as 2-MeImpG.

Purification and characterization of ATBP, a novel protein that binds to A/T stretches in three segments of the Sarcophaga lectin gene.

A DNA-binding protein for the Sarcophaga lectin gene, ATBP (A/T-stretches-binding protein) was purified to homogeneity from the nuclear extract of NIH-Sape-4 cells. The molecular mass of ATBP determined under denaturing conditions was 53 kDa, but its native molecular mass estimated by gel-filtration chromatography was 430 kDa, suggesting that it is an octamer of the 53-kDa subunit. This protein bound to at least three DNA fragments from the Sarcophaga lectin gene, two of them are in the 5'-upstream region and the other is in a region containing an intron. These fragments are very AT rich and inlaid with stretches of A or T residues (A/T stretches). ATBP was found to have affinity for poly[d(A-T)]. These results suggest that ATBP binds to A/T stretches in the three DNA fragments from this gene. Furthermore, longer DNA was found to be bound more effectively, suggesting that an octamer of the 53-kDa subunit has multiple binding sites for the DNA fragments and requires a relatively long DNA sequence for binding.

Mammalian Heterogeneous Ribonucleoprotein A1 and its Constituent Domains: Nucleic Acid Interaction, Structural Stability and Self-association

With a view toward further understanding the structure-function relationships of the eukaryotic heterogeneous ribonucleoprotein (hnRNP) A1, and in particular its multiplicity of nucleic acid-interactive domains, we have studied the nucleic acid binding properties of the globular N-domain (UP1) and sequence-repetitive, flexible C-domain, the thermal denaturation of UP1 and the concomitant effects of binding polynucleotide,and the self-associative properties of the full-length protein. Utilizing protein tryptophan fluorescence as a probe, polynucleotide binding was shown to stabilize UP1 against thermal unfolding. The denaturation profile of UP1-poly(thymidylic acid)complexes was biphasic, suggesting that unfolding of the two subdomains of UP1 can occur independently. This is in agreement with a previously proposed structure in which only one of the two UP1 subdomains binds the nucleic acid. The subdomains of UP1 can be prepared by controlled proteolysis of A1, further indicating that these two globular segments within A1 are connected by an exposed, flexible linkage. Circular dichroism measurements on UP1 confirm previous data that this portion of A1 binds single-stranded nucleic acids non-co-operatively. UP1 clearly shows a preference for single-stranded nucleic acids with a 2′-OH, since its affinity for poly(U) is three times higher than for poly(dU), and five times higher than its affinity for poly(2′-OCH 3U). The nucleic acid-interactive properties of the C-domain were further examined by preparing a synthetic peptide polymer ( M r≈ 12,000) containing about seven repeats of a 16-residue sequence, GNFGGGRGGNYGGSRG, which in turn comprises two copies of the C-terminal consensus, GN(F/Y)GG(G/S)RG. The polymer of this sequence exhibited significant affinity for the fluorescent polyribonucleotide, poly(ethenoadenylic acid), binding stoichiometrically at ≤ 0·2 M-Na +. Complex formation was accompanied by an increase in aggregate formation, as indicated by the appearance of scattering. For purposes of comparison, the data were analyzed via, the linear co-operative model of McGhee and von Hippel, though this model may not be fully descriptive of the protein-nucleic acid complex(es) formed in this case. In contrast to the non-co-operative binding mode of the UP1 domain, the C-polymer exhibited moderate co-operativity, comparable to that seen with full-length A1. Although addition of sufficient NaCl reversed the interaction, a sigmoidal binding isotherm could still be observe (with sufficient added polymer) at 0·8 M-NaCl. This suggests that non-electrostatic interactions contribute significantly to the free energy of binding. The peptide polymer did not exhibit any apparent specificity for single-stranded versus double-stranded and ribonucleic versus deoxyriblonucleic acids. The polymer catalyzed DNA interstrand annealing, an activity previously observed in full-length A1 and A1-derived C-terminal fragment. A non-repetitive synthetic peptide, containing only one copy of the 16-residues sequence, showed neither nucleic acid binding nor annealing activity. This suggests that the repetition of the consensus sequence is required for theses properties. Self-association of intact A1 was observed in the presence or absence of nucleic acids, and may be mediated by hydrophobic interactions residing in its C-terminal domain.

Modified Polyanionic Polymers for Enhanced Cell Membrane Interaction

The affinity of poly(maleic acid- alt-2-cyclohexyl-1,3-dioxepin-5- ene) [poly(MA-CDA)] for cell membranes was improved by grafting hydrophobic groups onto the polymer. The membrane affinity of these modified polyanionic polymers was characterized by their interaction with negatively charged lipo somes. The biological activity of the modified polymers in vitro was determined with cultured cell lines. The superoxide release from DMSO differentiated HL- 60 cells, stimulated by the modified poly(MA-CDA), was remarkable compared to the unmodified poly(MA-CDA). This higher activity may be due to the im proved affinity of the modified polymers for the cell membranes. The long-term cytotoxicity of the polymers was examined using J774 cells. It was observed that the polymers were cytotoxic at relatively high concentrations, and the cytotoxicity correlated with the improved membrane aflinity. In both in vitro tests, the molecular weight of the modified poly(MA-CDA) affected the biologi cal response. The higher activities were found for the lower molecular weight polymers.

A twenty-two-fold increase in the relative affinity of estrogen receptor to poly (dA-dC).poly (dG-dT) in the presence of polyamines

We studied the relative efficacy of polyamines to facilitate the binding of estrogen receptor to poly(dA-dC).poly(dG-dT). In the absence of polyamines, 1,400 micrograms/ml of this polynucleotide eluted 50% of bound estrogen receptor from DNA-cellulose. In contrast, 50% estrogen receptor was eluted by 65 micrograms/ml of poly(dA-dC).poly(dG-dT) complexed with 150 microM spermidine. Putrescine and spermine also enhanced the ability of poly(dA-dC).poly(dG-dT) to elute estrogen receptor, but the magnitude of the effect was not as high as that of spermidine. Control experiments with calf thymus DNA and poly(dA-dT).poly(dA-dT) showed 6- and 3-fold increase, respectively in their affinity for estrogen receptor in the presence of spermidine. The dramatic increase in the affinity of poly(dA-dC).poly(dG-dT) for estrogen receptor in the presence of polyamines might be a result of the conversion of the polynucleotide to the left-handed Z-DNA form. These results show that polyamines are capable of participating in estrogenic regulation of gene expression by altering the affinity of the receptor for specific DNA sequences.

Proteins from rat liver cytosol which stimulate mRNA transport. Purification and interactions with the nuclear envelope mRNA translocation system.

Two polysome-associated proteins with particular affinities for poly(A) have been purified from rat liver. These proteins stimulate the efflux of mRNA from isolated nuclei in conditions under which such efflux closely stimulates mRNA transport in vivo, and they are therefore considered as mRNA-transport-stimulatory proteins. Their interaction with the mRNA-translocation system in isolated nuclear envelopes has been studied. The results are generally consistent with the most recently proposed kinetic model of mRNA translocation. One protein, P58, has not been described previously. It inhibits the protein kinase that down-regulates the NTPase, it enhances the NTPase activity in both the presence and the absence of poly(A) and it seems to increase poly(A) binding in unphosphorylated, but not in phosphorylated, envelopes. The other protein, P31, which probably corresponds to the 35,000-Mr factor described by Webb and his colleagues, enhances the binding of poly(A) to the mRNA-binding site in the envelope, thus stimulating the phosphoprotein phosphatase and, in consequence, the NTPase. The possible physiological significance of these two proteins is discussed.

The in vitro interaction of naphthyridinomycin with deoxyribonucleic acids

The binding of naphthyridinomycin (NAP) to deoxyribonucleic acid was investigated using radioisotope labeled antibiotic. Dithiothreitol (DTT) enhances complex formation in a concentration dependent fashion but was found to be slightly inhibitory at concentrations above 10 mM. [C 3H 3]-NAP-DNA complexes, formed in the presence or absence of reducing reagents, were stable to Sephadex G-25 chromatography and precipitation with ethanol, indicating a strong bond formed between the drug and DNA. Time course studies showed that the difference between the binding of activated and non-activated antibiotic was a DTT-dependent burst. This was followed by a second phase of binding which was similar in both the activated and non-activated antibiotics. The activation of the antibiotic by DTT was a reversible reaction at pH 7.9. The activated form at pH 5.0 was extremely stable and did not revert to the unactivated form even after an 8-h incubation period. Antibiotic-DNA complex formation was pH independent between pH 5.0 and 7.0 for activated NAP. The non-activated antibiotic bound to DNA much better at pH 5.0 than at physiological pH values. Release of antibiotic from complexes (as followed by long term dialysis) formed in the presence of DTT and at pH 5.0 was biphasic, suggesting that the drug can bind to DNA in more than one way. A constant rate of antibiotic release was observed at pH 7.9 with or without DTT. At pH 2.0 and pH 12.0, greater than 95% of the antibiotic is released from the complexes. Most of the acid released antibiotic is NAP while most of the base released antibiotic had decomposed to a more polar compound. NAP binds well to calf thymus DNA, poly(dG) · poly(dC), and T 4 DNA but shows significantly less affinity for poly(dA) · poly(dT), poly(dA · dT) · poly(dA · dT), poly(dG), poly(dC), poly(dI) · poly(dC) or poly(dG · dC) · poly(dG · dC). This specificity of NAP for DNA is similar to that observed for the pyrrolo(1,4)benzodiazepine antibiotics and saframycin A and S; all of which bind to double stranded DNA through their carbinolamine or masked carbinolamine functionalities. Two mechanisms which can explain the need for activation of NAP are also proposed.