Biospectroscopy最新文献

{"title":"FTIR study of the nature of Na+ cation motion in gramicidin A","authors":"Franz Bartl,&nbsp;Bartosz Różalski,&nbsp;Grzegorz Schroeder,&nbsp;Bogumil Brzezinski,&nbsp;Georg Zundel","doi":"10.1002/(SICI)1520-6343(1999)5:5<284::AID-BSPY3>3.0.CO;2-4","DOIUrl":"10.1002/(SICI)1520-6343(1999)5:5<284::AID-BSPY3>3.0.CO;2-4","url":null,"abstract":"<p>The hydrated complex of gramicidin A with Na⁺ cations was studied by FTIR spectroscopy. The water bands observed in the FTIR spectrum are identical with those obtained for the hydrated gA–Li⁺ complexes. In the far infrared spectrum of the gA–Na⁺ complex an intense continuum was found indicating large Na⁺ polarizability of the gA channels. This Na⁺ polarizability arises, similarly as in the case of the Li⁺ complex, due to the fast fluctuation of the Na⁺ ions between two water molecules and four CO groups of the gA backbone. The much smaller barriers in the six minima Na⁺ potentials explain the much larger mobility of the Na⁺ when compared with the Li⁺ ions. © 1999 John Wiley &amp; Sons, Inc. Biospectroscopy 5: 284–288, 1999</p>","PeriodicalId":9037,"journal":{"name":"Biospectroscopy","volume":"5 5","pages":"284-288"},"PeriodicalIF":0.0,"publicationDate":"1999-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/(SICI)1520-6343(1999)5:5<284::AID-BSPY3>3.0.CO;2-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87318846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Infrared spectroscopy of human tissue. V. Infrared spectroscopic studies of myeloid leukemia (ML-1) cells at different phases of the cell cycle","authors":"Susie Boydston-White,&nbsp;Tamara Gopen,&nbsp;Sandra Houser,&nbsp;Jill Bargonetti,&nbsp;Max Diem","doi":"10.1002/(SICI)1520-6343(1999)5:4<219::AID-BSPY2>3.0.CO;2-O","DOIUrl":"10.1002/(SICI)1520-6343(1999)5:4<219::AID-BSPY2>3.0.CO;2-O","url":null,"abstract":"<p>Infrared spectra of myeloid leukemia (ML-1) cells are reported for cells derived from an asynchronous, exponentially growing culture, as well as for cells that were fractionated according to their stage within the cell division cycle. The observed results suggest that the cells' DNA is detectable by infrared spectroscopy mainly when the cell is in the S phase, during the replication of DNA. In the G1 and G2 phases, the DNA is so tightly packed in the nucleus that it appears opaque to infrared radiation. Consequently, the nucleic acid spectral contributions in the G1 and G2 phases would be mostly that of cytoplasmic RNA. These results suggest that infrared spectral changes observed earlier between normal and abnormal cells may have been due to different distributions of cells within the stages of the cell division cycle. © 1999 John Wiley &amp; Sons, Inc. Biospectroscopy 5: 219–227, 1999</p>","PeriodicalId":9037,"journal":{"name":"Biospectroscopy","volume":"5 4","pages":"219-227"},"PeriodicalIF":0.0,"publicationDate":"1999-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/(SICI)1520-6343(1999)5:4<219::AID-BSPY2>3.0.CO;2-O","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21342005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pharmacologic application of FTIR spectroscopy: Effect of ascorbic acid-induced free radicals on Deinococcus radiodurans","authors":"Anne-Marie Melin,&nbsp;Annie Perromat,&nbsp;Gérard Déléris","doi":"10.1002/(SICI)1520-6343(1999)5:4<229::AID-BSPY3>3.0.CO;2-I","DOIUrl":"10.1002/(SICI)1520-6343(1999)5:4<229::AID-BSPY3>3.0.CO;2-I","url":null,"abstract":"<p>Fourier transform infrared (FTIR) spectroscopy was used as a convenient and easy-to-run method to monitor radical-induced damage on the radiation-resistant <i>Deinococcus radiodurans</i> strain. Increasing concentrations of ascorbic acid added to the culture medium during the stationary phase produced striking changes in the infrared spectra. These changes especially occurred in the 1700–900 cm⁻¹ region, which is spectroscopically assigned to the amide I and II components, nucleotide bases, phosphodiester backbone and sugar rings, and were correlated with the oxidant effect of ascorbic acid. Thus, FTIR analysis allows a rapid characterization of the changes induced by ascorbic acid in the cell environment, which can be correlated in part with the generation of free radicals. Beyond a critical ascorbic acid concentration of 40 m<i>M</i>, these free radicals can cause severe damage to the biomolecular components, as soon as the antioxidant defenses of the bacterium are overwhelmed. © 1999 John Wiley &amp; Sons, Inc. Biospectroscopy 5: 229–236, 1999</p>","PeriodicalId":9037,"journal":{"name":"Biospectroscopy","volume":"5 4","pages":"229-236"},"PeriodicalIF":0.0,"publicationDate":"1999-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/(SICI)1520-6343(1999)5:4<229::AID-BSPY3>3.0.CO;2-I","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21342006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spectroscopic and ultrastructural comparative study of cystine calculi in humans and dogs","authors":"Elena Escolar,&nbsp;Juana Bellanato","doi":"10.1002/(SICI)1520-6343(1999)5:4<237::AID-BSPY4>3.0.CO;2-E","DOIUrl":"10.1002/(SICI)1520-6343(1999)5:4<237::AID-BSPY4>3.0.CO;2-E","url":null,"abstract":"<p>The careful analysis of cystine calculi may be important to detect the presence of other urinary alterations (such as hyperuricosuria, hypercalciuria, hyperoxaluria or bacterial infections) that coexist with cystinuria in many patients. For this reason, in the present study, 14 human and 17 canine cystine uroliths have been studied by infrared spectroscopy (IR), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). According to the infrared analysis, most of the human and canine stones were composed of nearly pure cystine. However, in these calculi of apparently pure cystine, the study by SEM and EDX showed in many cases the presence of small amounts of calcium apatite. The infrared study of several samples heated at 750°C confirmed the presence of phosphate, when it was difficult to detect this component in the spectra of the original samples owing to band overlapping. Other components detected in varying proportions in cystine calculi were magnesium ammonium phosphate hexahydrate (struvite), calcium hydrogen phosphate dihydrate (brushite), calcium oxalate (mono and/or dihydrate) and, in one case, a drug (oxolinic acid). © 1999 John Wiley &amp; Sons, Inc. Biospectroscopy 5: 237–242, 1999</p>","PeriodicalId":9037,"journal":{"name":"Biospectroscopy","volume":"5 4","pages":"237-242"},"PeriodicalIF":0.0,"publicationDate":"1999-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/(SICI)1520-6343(1999)5:4<237::AID-BSPY4>3.0.CO;2-E","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21341956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Circular dichroism spectroscopy analysis of conformational transitions of a 54 base pair DNA duplex composed of alternating CGCGCG and TATATA blocks","authors":"Jaroslav Kypr,&nbsp;Jiří Štěpán,&nbsp;Jana Chládková,&nbsp;Michaela Vorlíčková","doi":"10.1002/(SICI)1520-6343(1999)5:4<253::AID-BSPY6>3.0.CO;2-6","DOIUrl":"10.1002/(SICI)1520-6343(1999)5:4<253::AID-BSPY6>3.0.CO;2-6","url":null,"abstract":"<p>CD spectroscopy was used to analyze conformational properties of a self-complementary 54-mer DNA composed of alternating (CG)₃ and (TA)₃ hexamers. NaCl induced the Z-form in poly(GC), but the 54-mer remained the B-form under the same conditions. The B–Z transition was induced only after the addition of NiCl₂. However, the Z-form was adopted by the whole molecule, not by the (CG)₃ blocks alone. Two orders of magnitude higher concentrations of NiCl₂ were required to induce the Z-form in poly(AT). The Z-form was also induced in poly(GC) by CsF that switched poly(AT) into the X-form, which seems to be a solution counterpart of D-DNA. Under these conditions the CD spectrum of the 54-mer was consistent with the (TA)₃ blocks being in the X-form and the (CG)₃ blocks in the B-form. At high concentrations of ethanol or trifluoroethanol, poly(AT) was an A-form, while poly(GC) adopted either Z-form, A-form or Z′-form. At the high trifluoroethanol concentrations the 54-mer cooperatively switched into a conformation whose CD spectrum was most consistent with the A-form in the (TA)₃ blocks and the Z′-form in the (CG)₃ blocks. This suggests that the base pairs are tilted in the Z′-form as in the A-form. The present article illustrates that CD spectroscopy can provide interesting pieces of information about conformational isomerizations and coexistence of multiple conformations in DNA molecules containing blocks of different simple sequence repeats. © 1999 John Wiley &amp; Sons, Inc. Biospectroscopy 5: 253–262, 1999</p>","PeriodicalId":9037,"journal":{"name":"Biospectroscopy","volume":"5 4","pages":"253-262"},"PeriodicalIF":0.0,"publicationDate":"1999-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/(SICI)1520-6343(1999)5:4<253::AID-BSPY6>3.0.CO;2-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21341958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Raman and solid state 13C-NMR investigation of the structure of the 1 : 1 amorphous piroxicam : β-cyclodextrin inclusion compound","authors":"Enrico Redenti,&nbsp;Margherita Zanol,&nbsp;Paolo Ventura,&nbsp;Giovanni Fronza,&nbsp;Angiolina Comotti,&nbsp;Paola Taddei,&nbsp;Alessandro Bertoluzza","doi":"10.1002/(SICI)1520-6343(1999)5:4<243::AID-BSPY5>3.0.CO;2-C","DOIUrl":"10.1002/(SICI)1520-6343(1999)5:4<243::AID-BSPY5>3.0.CO;2-C","url":null,"abstract":"<p>The results of a Raman and solid state ¹³C-NMR spectroscopic investigation aimed at studying the conformation of piroxicam (P) and its interaction with β-cyclodextrin (βCD) in 1 : 1 amorphous PβCD inclusion compound are reported. The 1700–1200 cm⁻¹ FT-Raman and the ¹³C CP/MAS NMR spectra of 1 : 1 PβCD inclusion compound are discussed and assigned in comparison with those of the three main modifications of piroxicam (α, β, and monohydrate). The FT-Raman and ¹³C-NMR results show that in 1 : 1 PβCD inclusion compound piroxicam mainly assumes the zwitterionic structure typical of monohydrate, even if the presence of a different structure, that is, β form, is not excluded. Piroxicam monohydrate, differently from α and β forms, is characterized by a zwitterionic structure with an internal proton transfer and an increased charge delocalization, as shown by our spectroscopic results. The charge delocalization characteristic of this zwitterionic structure gives rise to the interaction with βCD via electrostatic and hydrogen bonds. The possibility of a host–guest interaction between piroxicam and βCD is not excluded; the guest molecule can be accommodated in βCD cavity by interaction via hydrophobic bonds. © 1999 John Wiley &amp; Sons, Inc. Biospectroscopy 5: 243–251, 1999</p>","PeriodicalId":9037,"journal":{"name":"Biospectroscopy","volume":"5 4","pages":"243-251"},"PeriodicalIF":0.0,"publicationDate":"1999-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/(SICI)1520-6343(1999)5:4<243::AID-BSPY5>3.0.CO;2-C","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21341957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molecular structure of 5-methyl thiophene acryloyl ethyl thiolester: A vibrational spectroscopic and density functional theory study","authors":"Deendyal Dinakarpandian,&nbsp;Paul R. Carey","doi":"10.1002/(SICI)1520-6343(1999)5:4<201::AID-BSPY1>3.0.CO;2-1","DOIUrl":"10.1002/(SICI)1520-6343(1999)5:4<201::AID-BSPY1>3.0.CO;2-1","url":null,"abstract":"<p>Enzyme-substrate intermediates involving the acyl group 5-methyl thiophene acryloyl (5-MTA) bound to the active site of an enzyme via a sulfur or selenium atom have been characterized by Raman spectroscopy (e.g., J. D. Doran and P. R. Carey, Biochemistry 1996, 35, 12495–12502, and M. J. O'Connor et al., J Amer Chem Soc 1996, 118, 239–240). Raman difference spectra reveal the Raman spectrum of the acyl group in the active site and, in turn, these can be used to probe acyl group conformation and active site forces and interactions. In order to improve the understanding of the relationship between conformational states and vibrational spectra of 5-MTA thiolesters, calculations based on a density functional theory analysis are undertaken for 5-methyl thiophene acryloyl ethyl ester. The calculations provide the precise geometries and energies of rotomers of 5-MTA ethyl thiolester involving rotational isomerism about the C<span></span>C single bonds flanking the ethylenic linkage and the S<span></span>C bond linking the ethyl group to the sulfur atom. The calculations also provide the vibrational spectrum for each conformer and these predictions are compared with the experimental Raman an IR data for the thiolester in carbon tetrachloride. Modes are identified that can act as conformational markers for isomerism about the C<span></span>C and S<span></span>C₂H₅ single bonds. These findings are used to identify the two conformational states giving rise to the Raman spectrum of the 5-MTA-S-enzyme formed by the viral cysteine protease HAV-3C. © 1999 John Wiley &amp; Sons, Inc. Biospectroscopy 5: 201–218, 1999</p>","PeriodicalId":9037,"journal":{"name":"Biospectroscopy","volume":"5 4","pages":"201-218"},"PeriodicalIF":0.0,"publicationDate":"1999-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/(SICI)1520-6343(1999)5:4<201::AID-BSPY1>3.0.CO;2-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21342004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Circular dichroism and molecular modeling of the E. coli TolA periplasmic domains","authors":"Rahmona Derouiche,&nbsp;Roland Lloubès,&nbsp;Sophie Sasso,&nbsp;Henri Bouteille,&nbsp;Razika Oughideni,&nbsp;Claude Lazdunski,&nbsp;Erwann Loret","doi":"10.1002/(SICI)1520-6343(1999)5:3<189::AID-BSPY8>3.0.CO;2-O","DOIUrl":"10.1002/(SICI)1520-6343(1999)5:3<189::AID-BSPY8>3.0.CO;2-O","url":null,"abstract":"<p>Colicins are killer proteins that use envelope proteins from the outer and the inner membranes to reach their cellular target in susceptible cells of <i>Escherichia coli</i>. Each group A colicin uses a combination of Tol proteins to cross the outer membrane of gram-negative bacteria and to exert their killing activity. The TolA protein, necessary for the import of all the group A colicins, is a 421-amino acid residue protein composed of three domains (TolAI, TolAII, and TolAIII). TolAIII interacts with the N-terminal domain of colicin A (AT1). Analytical ultracentrifugation reveals that TolAII and TolAIII are monomer structures, TolAII has an elongated structure, and TolAIII is rather globular. Circular dichroism (CD) spectra were done with TolAII-III, TolAII, TolAIII, AT1, and the AT1–TolAII-III complex. TolA CD spectra reveal the presence of α-helix structure in aqueous solution and the intensity of the α-helix signal is the highest with TolAII. Few structural changes are observed with the complex AT1–TolAII-III. Molecular modeling was done for TolAII-III, taking into account CD and ultracentrifugation data and show that domain II can adopt a barrel structure made of three twisted α-helices similar to coiled coil helices while domain III can adopt a globular structure. © 1999 John Wiley &amp; Sons, Inc. Biospectroscopy 5: 189–198, 1999</p>","PeriodicalId":9037,"journal":{"name":"Biospectroscopy","volume":"5 3","pages":"189-198"},"PeriodicalIF":0.0,"publicationDate":"1999-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/(SICI)1520-6343(1999)5:3<189::AID-BSPY8>3.0.CO;2-O","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21248172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lipid composition, membrane structure relationships in lens and muscle sarcoplasmic reticulum membranes","authors":"Douglas Borchman,&nbsp;Daxin Tang,&nbsp;Marta C. Yappert","doi":"10.1002/(SICI)1520-6343(1999)5:3<151::AID-BSPY5>3.0.CO;2-D","DOIUrl":"10.1002/(SICI)1520-6343(1999)5:3<151::AID-BSPY5>3.0.CO;2-D","url":null,"abstract":"<p>Membrane lipid composition varies in different tissues and species. Since a defined lipid composition is essential to the function of many membranes, the relationship between membrane lipid composition and structure was determined using infrared and Raman spectroscopy in four membranes containing a calcium pump: rabbit fast and slow twitch muscle sarcoplasmic reticulum and human and bovine lens fiber cell membranes. We found that membrane sphingolipid and phosphatidylcholine content were correlated to a decrease and increase, respectively, in the infrared lipid CH₂ symmetric stretching band frequency. We interpret the change in frequency as a change in lipid hydrocarbon chain structural order. This was confirmed by Raman order parameters. The high degree of hydrocarbon chain saturation found in the variable amide chains of sphingolipids is likely to account for this correlation. Lipid phase transition temperature and cooperativity also correlated to sphingolipid and phosphatidylcholine content, and are the forces defining the order in at physiological temperature in the samples studied. Ca²⁺-ATPase caused an increase in the CH₂ symmetric stretching frequency in fast twitch muscle sarcoplasmic reticulum (interpreted as an increase in hydrocarbon chain disorder), but had no effect on slow twitch muscle sarcoplasmic reticulum lipid hydrocarbon chain structure. In the natural systems studied, we find that it is the lipid hydrocarbon chain saturation that defines lipid hydrocarbon chain order. © 1999 John Wiley &amp; Sons, Inc. Biospectroscopy 5: 151–167, 1999</p>","PeriodicalId":9037,"journal":{"name":"Biospectroscopy","volume":"5 3","pages":"151-167"},"PeriodicalIF":0.0,"publicationDate":"1999-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/(SICI)1520-6343(1999)5:3<151::AID-BSPY5>3.0.CO;2-D","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21248169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"5,10,15,20-Tetrakis(4-N-methylpyridyl)porphyrinatopalladium(II) as a differentiation probe for sensing binding modes with B-DNA duplexes: Electronic MCD and CD spectra","authors":"N. Randy Barnes,&nbsp;Peter D. Stroud,&nbsp;Katie E. Robinson,&nbsp;Carl Horton,&nbsp;Anton F. Schreiner","doi":"10.1002/(SICI)1520-6343(1999)5:3<179::AID-BSPY7>3.0.CO;2-U","DOIUrl":"10.1002/(SICI)1520-6343(1999)5:3<179::AID-BSPY7>3.0.CO;2-U","url":null,"abstract":"<p>We report our detailed electronic MCD, CD, and optical spectroscopic measurements and analysis of the porphyrin Soret (<i>B</i>₀) region of four-coordinate 5,10,15,20-tetrakis(4-<i>N</i>-methylpyridyl)porphyrinatopalladium(II), PdP(4), and its bound states with B-DNA duplexes poly(A-T)₂, poly(G-C)₂, and calf thymus DNA (CT DNA). For system PdP(4)/poly(A-T)₂ it was possible to conclude that the porphyrin is bound edge-on in the major groove, specifically at the 5′AT3′ site. For this orientation the porphyrin's electric dipole transition moments (edtm), μ_<i>x</i> (most perturbed direction) and μ_<i>y</i> (least perturbed direction), have tilt angles α ∼ 90° and ∼ 45°, respectively, relative to the helix axis. It was further concluded from the <i>small shifts</i> of <i>B</i>₀ optical and MCD band intensities and wavelengths and from the net MCD (+) <i>A</i>-term <i>sign retention</i> upon binding that the porphyrin's frontier pπ MOs (1<i>a</i>_1<i>u</i> 3<i>a</i>_2<i>u</i> 4<i>e</i>_<i>g</i>) are only weakly perturbed by the heterocyclic bases of poly(A-T)₂, and therefore that the LUMO (4<i>e</i>_<i>g</i>) splitting is less than the |1<i>a</i>_1<i>u</i>−3<i>a</i>_2<i>u</i>| energy separation, ΔHOMO, that is, ΔLUMO &lt; ΔHOMO for the bound state in PdP(4)/poly(A-T)_2. For intercalation systems PdP(4)/poly(G-C)₂ and /CT DNA, with PdP(4) centered in the intercalation “pocket” and having two of its 4-<i>N</i>-methylpyridyls extending into each of the major and minor grooves, the edtms μ_<i>x</i> and μ_<i>y</i> were determined to be oriented perpendicular (γ ∼ 0°) and parallel (γ ∼ 90°) to the hydrogen bonds of the base pairs, respectively. Intercalation is characterized by a much stronger binding interaction, viz., the <i>B</i>₀ optical band and net MCD extrema wavelength shifts are relatively large, and the net MCD (+) <i>A</i>-term of PdP(4) is substantially quenched as it becomes the (−) pseudo-<i>A</i>-term of intercalated PdP(4)/poly(G-C)₂. This <i>A</i>-term sign reversal informs that the porphyrin MOs are so strongly perturbed by the GC base pairs that ΔLUMO &gt; ΔHOMO, which gives rise to a (−) pseudo-<i>A</i>-term. Also, the findings demonstrate (1) the potential of PdP(4) as a sensitive, discriminating analytical probe of DNA sequences and (2) the diagnostic capability of the composite of five spectra [net MCD, CD, and optical of free and bound PdP(4)] in differentiating the site and sequence selectivity and preferred binding mode of this porphyrin. © 1999 John Wiley &amp; Sons, Inc. Biospectroscopy 5: 179–188, 1999</p>","PeriodicalId":9037,"journal":{"name":"Biospectroscopy","volume":"5 3","pages":"179-188"},"PeriodicalIF":0.0,"publicationDate":"1999-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/(SICI)1520-6343(1999)5:3<179::AID-BSPY7>3.0.CO;2-U","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21248171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}