Infrared Spectroscopic Study and Mathematical Simulations of Carotid Atherosclerosis

BACKGROUND/AIM

The pathogenesis, treatment and prevention of atherosclerosis continue to be the subject of intensive research and study by the scientific community. Based on Fourier-transform infrared spectra and 3D-Doppler echogram, we attempted to develop a computational simulation model for predicting the association of atherosclerotic risk factors with pathogenic molecular structural changes.

MATERIALS AND METHODS

Atheromatic carotid arteries from 56 patients (60-85 years old) were used as samples. Color 3D-Doppler echogram screening was performed on all patients preoperatively. Each infrared spectrum consisted of 120 co-added spectra at a spectral resolution of 4 cm^-1 Results: The infrared spectral analysis reveals 'marker bands', such as the 1,744 cm^-1 band assigned to aldehyde formation and to the 'fingerprint' digital spectral region of 1,050-1,169 cm^-1, characteristic of the presence of advanced glycation end products (C-O-C). The accumulation of calcium phosphate salts increases the formation rate of stenosis. The critical point of stenosis risk starts at about 45%, while when stenosis is over 60-70%, the risk of ischemic stroke or other major adverse cardiovascular events increases dramatically.

CONCLUSION

Fourier-transform infrared spectroscopy and mathematical simulation models showed that carotid artery stenosis over 45% reduces the blood flow rate, while stenosis over 65% dramatically increases the hemodynamic disturbance, with a parallel increase the rate of ischemic stroke or other major adverse cardiovascular events.

Infrared study and computational simulations of coronary arteries atherosclerotic lesions for early diagnosis of disease progression

Introduction

Coronary artery atherosclerotic disease is the most common cardiovascular disease and bypass grafting surgery (CABG) is an effective treatment. However, the pathogenic mechanism of coronary arteries atherosclerosis and disease progression is not yet clear.

Purpose

The use of FT-IR spectroscopy, hyperspectral microscope and mathematical simulation models are some of the tools to predict the morphological and elasticity disorders in the vessel wall due to molecular structure changes.

Methods

Biopsies of atherosclerotic native coronary arteries from 54 patients (44–85 years), who underwent coronary endarterectomy during bypass grafting surgery (CABG), were examined ex vivo. The FT-IR-spectra were recorded with a Nicolet-6700 spectrometer. Morphological changes of atheromatic plaques were performed with SEM-EDX, Fei-Co. CytoVita-Olympus hyperspectral microscope was used to obtain the cells.

Results

FT-IR spectroscopy (Figure 1A) showed that the disease affects the protein folding, leading to amyloid formation (beta-sheets), lipid peroxidation and AGEs (Advanced Glycation end products) production. The detection of amorphous CaCO3 (1415 and 872 cm–1) deposits in high lipophilic regions was of high importance. Increased mineral concentration leads to increased formation of crystalline deposits, consisting of CaCO3, CaHPO4, Ca3(PO4)2 and inorganic hydroxyapatite, resulting in arterial stenosis. Hyperspectral images confirmed the formation of micelles (1) due to amyloidosis and calcified cells (2), in agreement with FT-IR, ImageJ analysis data. Mathematical simulation model based on finite element method (Figure 1E) showed that arterial wall damage and elasticity changes were not homogenous. This model provides the time of crystallization of the calcium salts, which play crucial role to stenosis.

Conclusions

FT-IR spectra showed that the formation of amorphous CaCO3 in the presence of Mg2+, in reach of oxidized lipids regions, inhibit the development of coronary artery stenosis. Excessive of Ca2+ efflux promotes the crystallinity of CaCO3 and Ca3(PO4)2 deposits, leading to the development of atherosclerotic plaques and coronary artery stenosis. Mathematical models approach in a much better way the progression of arterial atherosclerosis.

Funding Acknowledgement

Type of funding sources: None. Figure 1

Molecular structure analysis of ascending aorta aneurysm upon atherosclerosis

Background

The atherosclerotic ascending aorta could represent a potential source of emboli or could be an indicator of atherosclerosis in general with high mortality. The mechanism of aneurysm formation and atherosclerosis of the ascending aorta at the molecular level has not yet been clarified. To approach the mechanism of ascending aortic lesions and mineralization at a molecular level, we used the non-destructive FT-IR, Raman spectroscopy, SEM and Hypermicroscope.

Methods

Six ascending aorta biopsies were obtained from patients who underwent aortic valve replacement (AVR) cardiac surgery. CytoViva (einst inc) hyperspectral microscope was used to obtain the images of ascending aorta. The samples were dissolved in hexane on a microscope glass plate. The FT-IR and Raman spectra were recorded with Nicolet 6700 thermoshintific and micro-Raman Reinshaw (785nm, 145 mwatt), respectively. The architecture of ascending aorta biopsies was obtained by using scanning electron microscope (SEM of Fei Co) without any coating.

Results

FT-IR and Raman spectra showed changes arising from the increasing of lipophilic environment and aggregate formation (Fig. 1). The band at 1744 cm–1 is attributed to aldehyde CHO mode due to oxidation of lipids. The shifts of the bands of the amide I and amide II bands to lower are associated with protein damage, in agreement with SEM data. The bands at about 1170–1000 cm–1 resulted from the C-O-C of advanced glycation products as result of connecting tissues fragmentations and polymerization. The spectroscopic data were analogous with the lesions observed with SEM and hypermicroscopic images.

Conclusions

The present innovate molecular structure analysis showed that upon ascending aorta aneurysm development an excess of lipophilic aggregate formation and protein lesions, changing the elasticity of the aorta's wall. The released Ca2+ interacted mostly with carbonate-terminal of cellular protein chains accelerated the ascending aorta calcifications.

Figure 1. FT-IR and Raman spectra

Funding Acknowledgement

Type of funding source: None

Infrared and Raman Spectroscopic Studies of Molecular Disorders in Skin Cancer

AIM

To investigate the molecular structural disorders of cancerous skin.

MATERIALS AND METHODS

Human malignant melanoma and basal cell carcinoma biopsies were used for the investigation. Fourier transform infrared (FT-IR), Raman spectroscopy, and scanning electron microscopy were utilized. Spectral differences between healthy, basal cell carcinoma and melanoma tissues were recorded.

RESULTS

The FT-IR bands of vasCH2, vsCH2 and Raman vsCH3 of cell membrane lipids were increased in intensity in melanoma due to an increased lipophilic environment. The FT-IR band at 1,744 cm-1 assigned to malondialdehyde can be used as a band diagnostic of cancer progression. The amide I bands at 1,654 cm-1 and 1,650 cm-1 for Raman and FT-IR, respectively were broader in spectra from melanoma, reflecting changes of protein secondary structure from α-helix to β-sheet and random coil. The intensity of the FT-IR band at 1,046 cm-1 was increased in melanoma, suggesting glycosylation of the skin upon cancer development. Another band that might be considered as diagnostic was found at about 815 cm-1 in melanoma and was attributed to Z-DNA configuration. As far as we know, this is the first time that scanning electron microscopy revealed that metal components of titanium alloys from tooth implants were transferred to melanoma tissue taken from the back of one patient.

CONCLUSION

Vibrational spectroscopy highlighted increased glycosylation in melanoma.

FT-IR Spectroscopy Study in Early Diagnosis of Skin Cancer

BACKGROUND/AIM

Mid-infrared spectroscopy (4000-500 cm^-1) was used to analyze the spectral changes and differences of the characteristic absorption bands of the skin components due to cancer development for early clinical diagnosis.

MATERIALS AND METHODS

Human biopsies from basal cell carcinoma, malignant melanoma, and nevus were used, while normal skin tissue served as a control.

RESULTS

The high quality of Fourier-transform infrared (FT-IR) spectra showed that upon cancer development the intensity of the absorption band at approximately 3062 cm^-1 was increased, indicating that most of the proteins had the configuration of amide B and the β-sheet protein structure predominated. The stretching vibration bands of vCH₂ in the region 2950-2850 cm^-1 were increased in melanoma and nevus, while were less pronounced in basal cell carcinoma due to the increased lipophilic environment. In addition, the intensity of a new band at 1744 cm^-1, which is assigned to aldehyde, was increased in melanoma and nevus and appeared as a shoulder in the spectra of normal skin. The absorption band of amide I at 1650 cm^-1 was split into two bands, at 1650 cm^-1 and 1633 cm^-1, due to the presence of both α-helix and random coil protein conformations for melanoma and nevus. This was confirmed from the amide II band at 1550 cm^-1, which shifted to lower frequencies at 1536 cm^-1 and 1540 cm^-1 for basal cell carcinoma and melanoma, respectively, indicating a damage of the native structure of proteins. The bands at 841 and 815 cm^-1, which are assigned to B-DNA and Z-DNA, respectively, indicated that only the bands of the cancerous Z-DNA form are pronounced in melanoma, while in BCC both the characteristic bands of B-DNA and Z-DNA forms are found.

CONCLUSION

It is proposed that the bands described above could be used as "diagnostic marker" bands for DNA forms, in the diagnosis of skin cancer.

The effects of metal ion contaminants on the double stranded DNA helix and diseases

Mineral metal ions are essential for the maintenance of the reactions that regulate homeostasis and the functions of our body. It is known that the regulation of the neurodegenerative system depends directly on life metal ions, such as Na, K, Mg, Ca, Fe, Mo, Cu, Co, Zn, Cr, Mn, while the toxic metals Cd, Pb, Hg, etc disturb homeostasis, leading to diseases. Particularly significant is the effect of toxic metals on the double stranded forms of DNA and conformations. It was found that the toxic metal ions by reacting specifically with the nucleic bases and electrostatically with the negatively phosphate groups of the DNA backbone cause changes in the structure of the DNA double helix, leading to breaks of single or double strands. Accumulation of these defects affects the protecting systems of the body and induces mutations, eventually leading to serious diseases. There are many metal ions, such as Cr, Al, Cd, Cu, Ni, which by binding directly to DNA molecule or by developing oxidative stress increase the instability of DNA, promoting epigenetic changes that lead to DNA damage. Toxic metal ions induce indirect DNA damage and influence the gene stability by inactivating encoding proteins or by changing the redox potential and the signaling of metalloenzymes.

An FT-IR Spectral Analysis of the Effects of γ-Radiation on Normal and Cancerous Cartilage

In the present study we used non-distractive physicochemical methods to investigate the effect of γ-radiation on human articular cartilage. Comparison between the FT-IR (Fourier transform infrared) spectra before and after irradiation of the cartilage with different doses of radiation showed considerable changes in the spectra. It was found that for doses up to 2 Gy the collagen helices changed their structure from α-helix to random coil. By increasing the radiation dose it was found that the proteins' structure changed further to amyloid-like protein formation and to fragments of glycosaminoglycan chains, which were indicated in the IR spectra. Furthermore, comparison between the spectra of normal and irradiated cartilage, cancerous cartilage and cartilage from patients who received radiotherapy showed similarities in the spectra together with the formation of an aldehyde absorption band at 1740 cm(-1) suggesting that in all cases of cartilage examined,oxidative stress played major role in the damage progression of cartilage.

Resonance Raman Spectra and Structure of Partially Oxidized Magnus' Salt

The partially oxidized form of Magnus' salt has been studied by resonance Raman spectroscopy (RRS) and it has been established that the oxidized form is a chlorine bridged chain polymer. The spectra show intense progressions, υν, where ν, is the symmetric ···X-Pt(IV)-X··· stretching mode, and v the quantum number

Geographical information systems and air pollution simulation for Megalopolis' electric power plant in Peloponnese, Greece

The growth and sophistication of geographic information systems (GIS) have propelled us into a new era of environmental analyses. Air pollution is a growing concern in populated areas as many recent studies have associated high levels of pollution with increased illnesses and mortality. The study will focus on the toxicity levels incurred by radioactive lignite-burning Power Generation facilities located in Megalopolis, Greece. An estimate of pollution emissions followed by dispersion simulations for various atmospheric conditions will be given. The exercise will be integrated with a Geographical Information System (GIS) for defining the emission sources and visualizing the dispersion of pollutants over the geographical terrain. Data samples were collected from vegetation in the surrounding areas and analyzed for radioactivity. High energy levels (up to 4-5 times higher than recommended standards, (UNCEAR, 1982) were found in several samples containing (226)Ra, (232)Th, (234)Th, (40)K and (238)U. The study concludes that air quality and vegetation of the neighbouring areas is adversely affected by industrial waste. Greater pollution controls and air quality monitoring should be applied for the benefit and health of its citizens. Radioactivity in food and water and inhaled air become very dangerous for public health thus, the levels of radioactivity should be kept within UNCEAR 1982 limits.

Mortality and pollution in several Greek cities

This study examined the atmospheric pollution created by industry and traffic areas nearby the city of Kavala and the mortality of citizens in the region. The mortality data spanned over a period of 30 years. The statistical data on mortality was collected from 1968 to 1998. The causes of mortality analyzed in this study were cancer, cardiovascular deaths and pulmonary deaths. The results of this study were compared with other Greek cities. Air measurements were made over a period of 6 months and included levels of gaseous emissions as well as concentrations of Volatile Organic Compounds (VOCs), near the city of Kavala, where reservoirs of petroleum and exploitation of crude oil were present. Samples of air were collected from ambient surroundings near the industrial area and fuel oil facilities. The results obtained from the study indicated the presence of aromatic and aliphatic hydrocarbons and other gaseous pollutants such as, methane, o-, m-, p-xylene and ethylbenzene, etc. In some cases the levels exceeded the concentration limits specified by the air quality standards. Offensive odors were also detected (H2S). The study revealed that adverse environmental impact of air pollutants is a major concern in the industrial centers more than in the rural areas. This poses a threat to the public health and may induce disease and premature deaths. These air pollutants play an important role in air quality.

Magnesium-DNA interactions and the possible relation of magnesium to carcinogenesis. Irradiation and free radicals

Magnesium deficiency causes renal complications. The appearance of several diseases is related to its depletion in the human body. In radiotherapy, as well as in chemotherapy, especially in treatment of cancers with cis-platinum, hypomagnesaemia is observed. The site effects of chemotherapy that are due to hypomagnesaemia are decreased using Mg supplements. The role of magnesium in DNA stabilization is concentration dependent. At high concentrations there is an accumulation of Mg binding, which induces conformational changes leading to Z-DNA, while at low concentration there is deficiency and destabilization of DNA. The biological and clinical consequences of abnormal concentrations are DNA cleavage leading to diseases and cancer. Carcinogenesis and cell growth are also magnesium-ion concentration dependent. Several reports point out that the interaction of magnesium in the presence of other metal ions showed that there is synergism with Li and Mn, but there is magnesium antagonism in DNA binding with the essential metal ions in the order: Zn>Mg>Ca. In the case of toxic metals such as Cd, Ga and Ni there is also antagonism for DNA binding. It was found from radiolysis of deaerated aqueous solutions of the nucleoside 5'-guanosine monophosphate (5'-GMP) in the presence as well as in the absence of magnesium ions that, although the addition of hydroxyl radicals (*OH) has been increased by 2-fold, the opening of the imidazole ring of the guanine base was prevented. This effect was due to the binding of Mg2+ ions to N7 site of the molecule by stabilizing the five-member ring imitating cis-platinum. It was also observed using Fourier Transform Infrared spectroscopy, Raman spectroscopy and Fast Atom Bombardment mass spectrometry that *OH radicals subtract H atoms from the C1', C4' and C5' sites of the nucleotide. Irradiation of 5'-GMP in the presence of oxygen (2.5 x 10(-4) M) shows that magnesium is released from the complex. There is spectroscopic evidence that superoxide anions (O2-*) react with magnesium ions leading to magnesium release from the complex. From radiolysis data it was suggested that magnesium ions can act as radiosensitizers in the absence of oxygen, while in the presence of oxygen they act as protectors and stabilizers of DNA.

Copper and carcinogenesis

Metal ions play an important role in biological systems, and without their catalytic presence in trace or ultratrace amounts many essential co-factors for many biochemical reactions would not take place. However, they become toxic to cells when their concentrations surpass certain optimal (natural) levels. Copper is an essential metal. Catalytic copper, because of its mobilization and redox activity, is believed to play a central role in the formation of reactive oxygen species (ROS), such as O2-* and *OH radicals, that bind very fast to DNA, and produce damage by breaking the DNA strands or modifying the bases and/or deoxyribose leading to carcinogenesis. The chemistry and biochemistry of copper is briefly accounted together with its involvement in cancer and other diseases.

The role of free radical reactions with haemoglobin and thalassaemia

It is well known that all living systems depend on iron to transport (haemoglobin), store (myoglobin) and utilize (cytochromes, cytochrome oxide) oxygen for respiration. Iron is an essential component in the active sites of the enzyme that protects against oxidation, such as the iron superoxide dismutase, in bacteria and plants. In normal human plasma almost all iron loading of transferrin is 20-30% maximum. In this presentation we review and summarize recent developments in our understanding of iron transport and storage in living systems.

Biological implications of magnesium salts at the molecular level

The interaction of Mg2+ cations in biological systems is studied by using nucleic acid bases as the biological system. Magnesium salts, such as, MgCl2 6H2O, MgSO4. 7H2O and Mg(ClO4). XH2O have been employed in order to compare their complexation with cytosine and 1-methyl cytosine crystallize in water solutions. The reaction of the above magnesium salts with the two bases has been followed by attempting to crystallization the complexes formed at constant temperature and variable times of crystallization. The water solutions with the above reagents have also been followed by Fourier Transform infrared.

Molecular modeling of azole antifungal agents active against Candida albicans. 1. A comparative molecular field analysis study

A series of 56 azole antifungal agents belonging to chemically diverse families related to bifonazole, one of the antimycotic drugs of clinical use, were investigated using the comparative molecular field analysis (CoMFA) paradigm. The studied compounds, which have been already synthesized and reported to be active in vitro against Candida albicans, were divided into a training set and a test set. The training set consisted of 40 molecules from all the different structural classes. Due to the lack of experimental structural data on these derivatives, molecular mechanics techniques were used to obtain putative active conformations for all the compounds. the correctness of this molecular modeling work was confirmed a posteriori by comparison with structural data of the analog 2w obtained by X-ray crystallographic analysis (Massa, S.; et al. Eur. J. Med. Chem. 1992, 27, 495-502). Two different alignment rules of the training set molecules were used in this study and are based on the assumption that according to published results on azole antifungal agents, all the studied compounds exert their inhibitory activity through the coordination of their azole moiety to the protoporphyrin iron atom of the fungal lanosterol 14alpha-demethylase enzyme. The predictive ability of each resultant CoMFA model was evaluated using a test set consisting of 16 representative compounds that belong to all the different structural classes. The best 3D-quantitative structure-activity relationship model found yields significant cross-validated, conventional, and predictive r2 values equal to 0.57, 0.95, and 0.69, respectively. The average absolute error of predictions of this model is 0.30 log units, and the structural moieties of the studied antifungal agents which are thought to contribute to the biological activity were identified. The predictive capability of this model could be exploited in further synthetic studies on antifungal azoles. Furthermore, the results obtained by using two different alignments of the inhibitors suggest that the binding mode of these molecules involves both a coordination to the iron protoporphyrin atom and an additional, likewise relevant, hydrophobic interaction with the active site.

Design and properties of maxillofacial prosthetic materials

Maxillofacial reconstruction by prosthetic means is a valuable contribution that medicine offers to the public. Materials design and properties are the main problems faced by scientists in this field. Materials used for intraoral prostheses are not ideal, but they have been perfected to the point of practical use. Denture resins, gold, chromium-cobalt alloys, and porcelain are widely used and produce acceptable results in the oral cavity. In this review, the properties and performance of some polymeric materials used in maxillofacial prosthetics are discussed, and new trends in research and development are also reported.

Synthesis of diaminodideoxyalditol analogs of cisplatin as antitumor agents

Acyclic vicinal polyol complexes related to cisplatin were synthesized from D-mannitol by stereocontrolled manipulation of the hydroxy groups. Controlled cleavage of a 3,4-diazido hexitol gave the corresponding D-threitol and D-xylitol analogs, which were converted to their diamino platinum complexes. The antitumor activity of these compounds is reported.

Possible role of water structure in biological magnesium systems

Magnesium chloride-water solutions have been studied by Fourier Transform Infrared Spectroscopy (FT-IR) in the near infrared region, 5000-10,000 cm-1. The effect of the concentration of magnesium chloride and temperature on the solutions has been studied from the spectra and it is concluded that magnesium chloride modifies the structure of the bulk water. The important absorption bands of water at 5200 and 7020 cm-1 may be assigned to combination vibrations and overtones. They are shifted either by increasing the magnesium chloride concentration or the temperature. The hydrated magnesium ions, [Mg(H2O)6]2+, will most probably break important hydrogen bonds in the clusters of water (H2O)n, where n = 2, 3, 4, 5, 6.../forming new hydrogen bonds in the presence of hexa-aquated magnesium cations. FAB mass spectra also suggest the formation of hydrated magnesium cations, Mg (H2O)6(2+).

The dose rate effects on the in vitro radiolysis products of magnesium-guanosine-5'-monophosphate complexes in aqueous solutions

This study examined the effects on the radiolysis of magnesium-guanosine-5'-monophosphate complexes in deaerated aqueous solutions, investigated by Fourier transform infrared (FT-IR) spectroscopy. It was found that when the system was irradiated with a dose rate of 500 rad/min (low dose rate), the OH radicals, H atoms and hydrated electrons (eaq-) produced from radiolysis of water reacted mainly by addition to the double bonds C4 = C5 and N7 = C8 of guanine. When the dose rate was 23,800 rad/min (high dose rate) the electrons reacted further with the complex by addition to the carbonyl group, C6 = O, of guanine.

Radiolysis of 4-benzylideneamino-2,2,6,6-tetramethylpiperidine-1-oxyl (BAPO) in aqueous didodecyldimethyl-ammonium bromide (DDAB) membrane mimetic systems

The influence of solubilisation upon the reactivity of the nitroxyl BAPO with the free radicals produced in irradiated vesicle systems was investigated. The decomposition yield G(-BAPO) determined in didodecyldimethyl-ammonium bromide (DDAB) vesicle systems was found to be only 0.04, while in homogeneous aqueous solutions a value of 1.50 was observed. These results, as well as the EPR spectra of irradiated and nonirradiated samples, lead to the conclusion that BAPO is localized in the interior of the bilayer. This behavior is consistent with the hydrophobic character of the nitroxyl molecule due to its benzylidene group.

Radiolysis of 4-benzylideneamino-2,2,6,6-tetramethylpiperidine-1-oxyl (BAPO) and 3-carboxamido-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl (CATPO) in aqueous solutions

The mechanism of the gamma-radiolysis of the free nitroxyl radicals BAPO and CATPO in neutral deaerated as well as in N2O-saturated aqueous solutions was investigated. The decomposition of BAPO and CATPO was followed spectrophotometrically by measuring the absorbance at 249 and 233 nm, respectively. The yields G(-BAPO) and G(-CATPO) observed under several conditions are reported and discussed in relation to the yield of OH radicals, H atoms and e-aq, produced in irradiated aqueous solutions. It was found, on the analogy of other nitroxyls, that the corresponding hydroxylamines were formed when BAPO and CATPO react with H atoms, e-aq and hydroxyalkyl radicals. The H atoms and e-aq also react partly with BAPO and CATPO by addition to the aromatic nucleus and by elimination of NH3, respectively. The OH radicals react with BAPO by addition to the aromatic nucleus and by abstraction of H atoms from the 3 or 5 positions or from the methyl groups of the 2 or 6 positions. The reaction of OH radicals with CATPO consists in the abstraction of H atoms from the 3 or 4 positions or from the methyl groups of the 2 or 5 positions. The EPR spectra suggest that in both nitroxyls the final radiolysis products are stable biradicals and other paramagnetic compounds.

Synthesis, structure, proton-nuclear magnetic resonance, and Fourier transform infrared spectroscopy of several transition and nontransition metal–adenosine-5-triphosphate complexes

Several complexes of adenosine-5-triphosphate disodium salt (Na2H2ATP) with the metal ions, Na+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, Cu2+, and cis- and trans-Pt(NH3)2Cl2 and K2PtCl4 at pH = 3.5 and 7.2 have been isolated, identified, and studied. Marked spectral similarities have been observed for the structurally known metal–phosphate bonded compounds, [Cu(H2ATP)(phen)]2•7H2O and [Zn(H2ATP)(bipy)]2•4H2O and all the metal–ATP complexes studied here, except the Pt–ATP complexes. The metal binding is through the α, β, and γ phosphate oxygen atoms when the N1-position of adenine is protonated. Spectral changes have also been observed for the Pt–ATP complexes in which there is a Pt–N7 and –N1 coordination. The sugar pucker in the Na2H2ATP•3H2O crystal dimers is C3′-endo–anti (in one) and C2′-endo–anti (in the other) with a characteristic infrared band at 818 cm−1. In the corresponding Cu2+ and Zn2+ complexes the sugar has C3′-endo–anti conformation with the marker band at about 814 cm−1. The C2′-endo–anti conformation is observed for all the metal–ATP complexes prepared here with a marker band at 825–822 cm−1.

An FT-IR study of DNA and RNA conformational transitions at low temperatures

Fourier Transform Infrared (FT-IR) spectra of solid samples of DNA and RNA obtained from freeze-drying at solid CO2 and liquid nitrogen temperatures, have been recorded and correlation between the conformational transitions and spectral changes is proposed. It is concluded that an equilibrium exists between A, B and Z conformations at low temperatures for the DNA molecule, which is temperature dependent, whereas the RNA molecule exhibits only the A conformation. The results have been compared with the metal-adducts of DNA and RNA, where one of the conformations is predominant. Marker infrared bands for the B conformer have been found to be the strong band at 825 cm-1 (sugar conformer mode) and a band with medium intensity at 690 cm-1 (guanine breathing mode). The A conformation showed characteristic bands at 810 and 675 cm-1. The B to Z conformational transition was characterized by the strong absorption bands near 820-810 cm-1 and at 665-600 cm-1.

Magnesium – nucleotide interaction. Synthesis, structure, 1H, 13C nuclear magnetic resonance and Fourier transform infrared studies of Mg-inosine-5′-monophosphate complexes

The reaction of inosine-5′-monophosphate acid (IMPH2) with hydrated magnesium chloride MgCl2•6H2O gives complexes of the type Mg(IMP)•5H2O and Mg2(IMP)3•15H2O. The FT-IR spectra of Mg(IMP)•5H2O in the region 1800–400 cm−1 showed marked similarities with that of the structurally characterized N7-bound Ni(IMP)•5H2O and Co(IMP)•5H2O complexes, while Mg2(IMP)3•15H2O exhibited distinct spectral similarities with the known Cd2(IMP)3•12H2O and Ca(IMP)•6.5H2O compounds, where a direct metal–phosphate and metal–sugar binding as well as metal–N7-coordination has been shown crystallographically. The Mg(II) ion in Mg(IMP)•5H2O is N7-bound with an indirect metal–phosphate and metal–carbonyl interaction through a coordinated water molecule and in the Mg2(IMP)3•15H2O compound it binds directly to the phosphate and to the sugar moiety as well as to the N7-site of the purine ring system.

Flexibility of DNA and RNA upon binding to different metal cations. An investigation of the B to A to Z conformational transition by Fourier transform infrared spectroscopy

The interaction of DNA and RNA with Cu(II), Mg(II), [Co(NH3)6]3+ [Co(NH3)5Cl]2+ chlorides and, cis- and trans-Pt(NH3)2Cl2 (CIS-DDP, trans-DDP) has been studied by Fourier Transform Infrared (FT-IR) spectroscopy and a correlation between metal-base binding and conformational transitions in the sugar pucker has been established. It has been found that RNA did not change from A-form on complexation with metals, whereas DNA exhibited a B to Z transition. The marker bands for the A-form (C3'-endo-anti conformation) were found to be near 810-816 cm-1, while the bands at 825 and 690 cm-1 are marker bands for the B-conformation (C2'-endo, anti). The B to Z (C3'-endo. syn conformation) transition is characterized by the shift of the band at 825 cm-1 to 810-816 cm-1 and the shift of the guanine band at 690 cm-1 to about 600-624 cm-1.

An FT-ir study of cis study of trans-dichlorodiammineplatinum(II) bound to inosine-5′-monophosphate

Inosine-5′-monophosphate disodium salt (5′-IMPNa2) reacts with cis-dichlorodiammineplatinum(II) (cis-DDP) and its trans-isomer (trans-DDP) to give complexes of the type cis- and trans-Pt(NH3)2(IMPNa2)nCl2•xH2O, n = 1 or 2 and Pt(IMPNa2)nCl2•xH2O, where n = 1, 2, or 3 and x = 0–6. In the 1:2 platinum complexes the nucleotide binds only to the N7-atom of the purine ring system, while in the 1:1 metal complexes there is indication for Pt–carbonyl interaction (bridging or chelation) in addition to the N7-bonding at neutral pH values with cis-DDP.Solution FT-ir studies (H2O and D2O) showed that the 1:1 species formed with cis-DDP at neutral pH's behaved differently from those with trans-DDP. The carbonyl stretching vibration of the free base at 1685 cm−1 (H2O) and 1670 cm−1 (D2O) exhibited marked spectral changes in intensity, shifting, and shape upon complexation, whereas the reaction with the trans-isomer produced only slight perturbations in the above region.

A Fourier transform infrared study of the electrophilic attack at the N7-site of guanosine-5′-monophosphate

Fourier transform infrared spectra of several N7-bound cations of guanosine-5′monophosphate disodium salt (5′-GMPNa2), such as N7-H+GMP, N7-MeGMP, and N7-MGMP, where Me = CH3+ and M = divalent metal ions, Cd, Mn, Co, Ni, Cu, Pt, and Mg, have been recorded and a correlation between the spectral changes and the nature of the electrophile (H+, CH3+, and M2+) bound has been established. Spectroscopic evidence shows that methylation of the N7-position of 5′-GMPNa2 causes larger perturbation on the guanine ring system than protonation or metalation, in the order Me+ > H+ > M2+. The effect of an N7-electrophilic attack on the vibrational frequencies of the purine, the sugar, and the phosphate group is discussed.

Fourier transform infrared spectra of cells treated with the drug adriamycin

Fourier Transform Infrared Spectroscopy (FT-IR) is used to study the interaction of adriamycin molecule with DNA and/or cells. For the drug-DNA complexes, the data show that adriamycin interacts not only with the bases pair but also with the sugar-phosphate of DNA within intercalating process. In the case of treated tumor cells, spectra suggest that adriamycin could be interacting also with the proteins of the membrane. The obtained results show that FT-IR is a powerful technique in the study of biological system, say cells.

Platinum(II) and magnesium(II) nucleotide complexes. Synthesis, FT-ir spectra, and structural properties

Guanosine-5′-monophosphate (5′-GMP) reacts with Pt(II) and Mg(II) metal ions to give complexes of the type Pt(5′-GMP)nCl2•xH2O, cis- and trans-[Pt(NH3)2(5′-GMP)2]Cl2•xH2O and Mg(5'-GMP2)•xH2O, where n = 1, 2, 3, 4 and x = 4–10.Spectroscopic and chemical evidence showed marked similarities with those of the structurally known N7-bonded 5′-GMP complexes of Mn(II), Co(II), Ni(II), Cu(II), and Cd(II) metal ions. Therefore, Pt(II) and Mg(II) are also found to be N7-bonded in these series of nucleotide complexes.The direct phosphate coordination was observed in Mg(II) nucleotide complexes obtained from acidic solution, whereas Mg(II) complexes prepared from neutral solution showed no direct phosphate–Mg(II) interaction. Pt(II) complexes exhibited no direct phosphate metal bonding, while the possibility of an indirect Pt(II)–phosphate interaction through a hydrogen-bonded water molecule can be proposed here.