Effect of dioxane on the structure and hydration–dehydration of α-chymotrypsin as measured by FTIR spectroscopy

A new experimental approach based on FTIR spectroscopic measurements was proposed to study simultaneously the adsorption/desorption of water and organic solvent on solid enzyme and corresponding changes in the enzyme secondary structure in the water activity range from 0 to 1.0 at 25 °C. The effect of dioxane on the hydration/dehydration and structure of bovine pancreatic α-chymotrypsin (CT) was characterized by means of this approach. Dioxane sorption exhibits pronounced hysteresis. No sorbed dioxane was observed at low water activities (a_w < 0.5) during hydration. At a_w about 0.5, a sharp increase in the amount of sorbed dioxane was observed. Dioxane sorption isotherm obtained during dehydration resembles a smooth curve. In this case, CT binds about 150 mol dioxane/mol enzyme at the lowest water activities. Three different effects of dioxane on the water binding by the initially dried CT were observed. At a_w < 0.5, water adsorption is similar in the presence and absence of dioxane. It was concluded that the presence of dioxane has little effect on the interaction between enzyme and tightly bound water at low a_w. At a_w > 0.5, dioxane increases the amount of water bound by CT during hydration. This behavior was interpreted as a dioxane-assisted effect on water binding. Upon dehydration at low water activities, dioxane decreases the water content at a given a_w. This behavior suggests that the suppression in the uptake of water during dehydration may be due to a competition for water-binding sites on chymotrypsin by dioxane. Changes in the secondary structure of CT were determined from infrared spectra by analyzing the structure of amide I band. Dioxane induced a strong band at 1628 cm^?1 that was assigned to the intermolecular β-sheet aggregation. Changes in the intensity of the 1628 cm^?1 band agree well with changes in the dioxane sorption by CT. An explanation of the dioxane effect on the CT hydration and structure was provided on the basis of hypothesis on water-assisted disruption of polar contacts in the solid enzyme. The reported results demonstrate that the hydration and structure of α-chymotrypsin depend markedly on how enzyme has been hydrated — whether in the presence or in the absence of organic solvent. A qualitative model was proposed to classify the effect of hydration history on the enzyme activity-a_w profiles.     

I.r. spectroscopic determination of the degree of substitution of benzyl chitins

I.r. spectroscopy (the KBr pressed disc method) has been successfully used for the determination of degree of benzylation in chitin. The band at 1550 cm⁻¹ was assigned an internal standard and the 700 cm⁻¹ band was assigned an analytic band. Degree of substitution look up the relative curve of ratio of A₇₀₀/A₁₅₅₀ against the degree of substitution.     

Low-temperature IR spectroscopy reveals four stages of water loss during lyophilization of hen egg white lysozyme

Water loss during lyophilization of a 49.4 mg/mL solution of lysozyme in D₂O was studied with ir spectroscopy using a low-temperature, single reflection, horizontal, attenuated, total reflectance accessory. Four regions of water loss were identified and assignable to different forms of bound water. The amide I band begins to shift to higher frequency while the amide II concurrently shifts to lower frequency and broadens after the first stage of water loss (sublimation) at ?10°C. Additionally, the carboxylate band (at 1584 cm^?1) shifts slightly to lower frequency. A second stage at 17°C is characterized by continued shifts in the carboxylate and amide II bands to low frequency, further broadening in the amide II and greater shift to high frequency in the amide I (ascribed to the removal of periphery water around the protein). At the third stage of water loss, the carboxylate band decreases substantially in relative absorbance (consistent with the removal of water from the carbonyl backbone). In the fourth and last stage, the carboxylate band nearly disappears and water loss is very slow. Based upon a final level of hydration of 0.037 h, the last stage corresponds to 25% completion of the removal of water associated with ionizable side chains. From start to finish, the amide I shifts 9 cm^?1 to higher frequency. © 1994 John Wiley & Sons, Inc.     

The origin of the A to B transition in DNA fibers and films

We have studied the hydration of Na-DNA and Li-DNA fibers and films, measuring water contents, x-ray fiber diffraction patterns, low-frequency Raman spectra (below 100 cm^?1), high-frequency Raman spectra (600–1000 cm^?1), and swelling, as a function of relative humidity. Most samples gain weight equilibrium (though not conformational equilibrium) in one day. The volume occupied by a base pair as the DNA is hydrated (obtained from the x-ray and swelling data) shows anomalies for the case of Na-DNA in the region where the A-form occurs. Our Raman and x-ray data reproduce the well-known features of the established conformational transitions, but we find evidence in the Raman spectra and optical properties of a transition to what may be a disordered B-like conformation in Na-DNA below 40% relative humidity. We have studied the effects of crystallinity on the A to B transition. We find that the transition to the B-form is impeded in highly crystalline samples. In most samples, the transition occurs in three days (after putting the sample at 92% relative humidity) but in highly crystalline samples, the transition may take months. By comparing the high-frequency Raman spectra of highly ordered and disordered films, we show that the extent of crystallinity controls the amount of A-DNA formed when ethanol is used to dehydrate the films. We show that rapid dehydration (by laser heating) does not result in a B to A transition. A fiber that gives A-type x-ray reflections probably contains B-like material in noncrystalline regions. The low-frequency Raman spectrum is dominated by a band at about 25 cm^?1 in both Na- and Li-DNA. Another band is seen near 35 cm^?1 in Na-DNA at humidities where the sample is in the A-form. In contrast to earlier reports, we find that the Raman intensity does not depend on fiber orientation relative to the scattering vector. The “35-cm^?1” band is largely depolarized (i.e. vertical polarization incident and horizontal polarization scattered, VH, or vice versa, HV) while the “25-cm^?1” band appears in both VV, VH and HV polarizations. These bands are all weaker in HH polarization. The “25-cm^?1” band may be due to a shearing motion of the phosphates and their associated counterions, while the “35-cm^?1” band may be characteristic of A-DNA crystallites. We consider mass-loading, relaxational coupling to the hydration shell, and softening of interatomic potentials as possible explanations of the observed softening of the low-frequency Raman bands on hydration. Relaxation data suggest that the added water binds tightly (on these time scales) and a mass-loading model accounts for the observed softening rather well. We conclude that the A to B transition is not driven by softening of the “25-cm^?1” band. Rather, it is most probably a consequence of crystal-packing forces, with the more regular A-form favored in crystals when these forces are strong.     

Characterization of DNA structures by laser Raman spectroscopy

Oriented fibers drawn from aqueous gels of calf-thymus DNA were maintained at constant relative humidites of 75 and 92% to yield canonical A-DNA and B-DNA structures, respectively. Raman spectra of the two forms of DNA were recorded over the spectral range 300–4000 cm^?1. The authenticated DNA fibers were deuterated in hygrostatic cells containing D₂O at appropriate relative humidities, and the corresponding spectra of deuterated DNAs were also obtained. The spectra reveal all of the Raman scattering frequencies and intensities characteristic of A- and B-DNA structures in both nondeuterated and deuterated froms, as well as the frequencies and intensities of adsorbed solvent molecules from which the hydration content of DNA fibers can be calculated. Numerous conformation-sensitive vibrational modes of DNA bases and phosphate groups have been identified throughout the 300–1700-cm^?1 interval. Evidence has also been obtained for conformation sensitivity of deoxyribosyl CH stretching modes in the 2800–3000-cm^?1 region. Raman lines of both the backbone and the bases are proposed as convenient indicators of A- and B-DNA structures. The results are extended to Z-DNA models investigated previously. Some implications of these findings for the determination of DNA or RNA structure from Raman spectra of nucleoproteins and viruses are considered.     

Water state and diffusion through lipid bilayers: Effect of hydration degree

The dependences of adsorbed water state (obtained from the variations in ¹H NMR spectra with the angle between the bilayer normal and magnetic field direction) and water diffusion along the bilayer normal (measured using pulsed field gradient ¹H NMR) on hydration degree have been studied in macroscopically oriented bilayers of dioleoylphosphatidylcholine. The angle dependences of the shape of NMR spectrum are qualitatively different only for water concentrations higher and lower than that achieved by hydration from saturated vapors (χ_eq, about 23%). At concentrations lower than χ_eq, all water in the sample either makes the hydration shells of the lipid polar heads or is in fast exchange with the shell water, so the spin-echo signal from water is detected only within a narrow range of angles close to the magic angle, 54.7°. At concentration exceeding χ_eq, the spin-echo signal from water is retained at all orientations, suggesting that a portion of water between bilayers (quasi-free water) slowly exchanges with water bound to the polar heads. There is an inverse dependence of the coefficient of water self-diffusion through the bilayer system on the hydration degree, which is described in the Tanner model with account of water self-diffusion in the hydrophobic part of the bilayer. Bilayer permeability, distribution coefficient of molecules between aqueous and lipid phases, and water self-diffusion coefficient in the hydrophobic region of the bilayer are estimated.     

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

Abstract

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 (C′₃-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 (C′₂-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.     

Ultraviolet circular dichroism of polyproline and oriented collagen

The ultraviolet absorption, linear dichroism, circular dichroism, and oriented circular dichroism of collagen are reported and the spectra are resolved into a self-consistent set of bands in accord with exciton theory. The parallel band at 200 nm has 40% of the π → π* intensity; the perpendicular band is placed at 189 nm yielding a splitting of 2700 cm^?1. The circular dichroism is resolved into two Gaussians at λ_∥ and λ_τ (rotational strengths +14 × 10^?40 and ?32 × 10^?40 esu². cm²) plus a large non-Gaussian (“helix”) band with ampplitude ?25,000° at 201 nm. These data appear to be in reasonably good accord with recent calculations. Measurements of the absorption, linear dichroism and circular dichroism of polyproline I and II are also reported and are resolved into their component bands. Polyproline I is in good accord with exciton theory, whereas polyproline II remains unsatisfactory.     

An X-ray diffraction study of poly-L-homoarginine hydrochloride.

An X-ray study of the synthetic polypeptide poly(L -homoarginine hydrochloride) has been made to investigate whether, like the chemically related polypeptides poly(L -lysine hydrochloride), poly(L -arginine hydrochloride), and poly(L -ornithine hydrobromide), it can undergo conformational transitions merely from variations in its degree of hydration. X-ray photographs of powder and oriented specimens containing one to 15 molecules of water per L -homoarginine hydrochloride residue showed that this polymer forms only a β-pleated-sheet structure. The pleated sheets, formed by antiparallel polypeptide chains hydrogen-bonded to each other, are piled up along the b axis in an alternating sequence (“sandwich structure”). This structure did not appreciably change with variations of the degree of hydration, and the observed reflections at 56% relative humidity (1.8 molecules of water per residue) could be indexed satisfactorily in terms of a monoclinic unit cell, of space group P2₁, with a = 9.34 Å, b = 40.07 Å, c = 6.94 Å, and γ = 106°. These dimensions are shown by models to be compatible with the proposed structure, and the calculated density of 1.27 g/cm³ agrees well with the experimental value of 1.29 g/cm³. Removal of the last molecule of water results in a very diffuse pattern, while specimens containing 20 molecules of water per residue show only reflections due to water.     

A Brillouin scattering study of the hydration of Li- and Na-DNA films

We have used Brillouin spectroscopy to study the velocities and attenuation of acoustic phonons in wet-spun films of Na-DNA and Li-DNA as a function of the degree of hydration at room temperature. Our data for the longitudinal acoustic (LA) phonon velocity vs water content display several interesting features and reveal effects that we can model at the atomic level as interhelical bond softening and relaxation of the hydration shell. The model for interhelical softening makes use of other physical parameters of these films, which we have determined by gravimetric, x-ray, and optical microscopy studies. We extract intrinsic elastic constants for hydrated Na-DNA molecules of c₁₁ ? 8.0 × 10¹⁰ dynes/cm² and c₃₃ ? 5.7 × 10¹⁰ dynes/cm², which corresponds to a Young's modulus, E ? 1.1 × 10¹⁰ dynes/cm² (with Poisson's ratio, σ = 0.44). The negative velocity anisotropy of the LA phonons indicates that neighboring DNA molecules are held together by strong interhelical bonds in the solid state. The LA phonon attenuation data can be understood by the relaxational model in which the acoustic phonon is coupled to a relaxation mode of the water molecules. Na-DNA undergoes the A to B phase transition at a relative humidity (rh) of 92% while Li-DNA (which remains in the B form in this range) decrystallizes at an rh of 84%. We find that our Brillouin results for Na- and Li-DNA are remarkably similar, indicating that the A to B phase transition does not play an important role in determining the acoustic properties of these two types of DNA.     

On transverse ordering in biomembranes by Raman spectroscopy

Computer simulation analysis of the structure sensitive features in the Raman spectrum of aqueous dipalmitoyl phosphatidylcholine (DPPC) multilayers was made for the 1000–1200 cm₋₁ region. The composite triplet was resolved into 4 Lorentzian bands with the possibility to follow their parameters (amplitude, width and position) in the temperature interval 25–60°C. The analysis reveals the apparent inward shift of the 1130 and 1065 cm⁻¹ bands towards both sides of the broad intense 1087 cm⁻¹ feature which is due to the relative changes in amplitudes of these bands in the course of the lipid phase transition. The more accurate method for the evaluation of the trans order parameter (S_trans) confirms the underestimation of the trans segment content above the phase transition temperature when using both the relative amplitude and area of the 1130 cm⁻¹ band for the quantitative characterization of chain conformation. Calculated changes in the bilayer thickness following the frequency shift of the 1100 cm⁻¹ band are in good agreement with the previously reported deuterium NMR data and X-ray diffraction studies.     

Subpicosecond dynamics in nucleotides measured by spontaneous Raman spectroscopy

The band widths in Raman spectra are sensitive to dynamics active on a time scale from 0.1 to 10 ps. The band widths of nucleotide vibrations and their dependence on temperature, concentration, and structure are reported. From the experimental band widths and second moments, it is derived that the adenine vibrations at 725, 1336, 1480, and 1575 cm⁻¹, and the uracil vibration at 787 cm⁻¹, are in the fast modulation limit. The correlation times of the perturbations are faster than 0.4 ps. Thermal melting of the helical structure in polynucleotides results in larger band widths, due to an increase in vibrational dephasing and energy relaxation as a consequence of the increased interaction of the base moieties with the solvent molecules. The band width of the 725 cm⁻¹ adenine vibration is dependent on the type and structure of the backbone. It is found to be perturbed by movements of the sugar-phosphate moiety relative to the base. The band width of the 1575 cm⁻¹ adenine vibration is found to be sensitive to the base-pairing interaction. From a comparison of the band widths in polynucleotides with a different base sequence (homopolymer vs alternating purine-pyrimidine sequence), it is concluded that resonant vibrational energy transfer between the base molecules is not important as a relaxation process for the vibrational band widths of nucleotides. Several theoretical models for the interpretation of band widths are discussed. The theory does not take into account the strong hydrogen-bonding nature water and hence fails to describe the observations in nucleotide-water systems. The bands of the carbonyl stretching vibrations are inhomogeneously broadened. The carbonyl groups have a strong dipolar interaction with the polar water molecules and are therefore strongly perturbed by coupling to the heatbath via hydrogen bonds. © 1997 John Wiley & Sons, Inc. Biopoly 41: 751–763, 1997     

One‐Step Controllable Synthesis of Catalytic Ni4Mo/MoOx/Cu Nanointerfaces for Highly Efficient Water Reduction

Currently, in addition to the electroactive non‐noble metal water‐splitting electrocatalysts, a scalable synthetic route and simple activity enhancement strategy is also urgently needed. In particular, the well‐controlled synthesis of the well‐recognized metal–metal nanointer face in a single step remains a key challenge. Here, the synthesis of Cu‐supported Ni₄Mo nanodots on MoO_x nanosheets (Ni₄Mo/MoO_x) with controllable Ni₄Mo particle size and d‐band structure is reported via a facile one‐step electrodeposition process. Density functional theory (DFT) calculations reveal that the active open‐shell effect from Ni‐3d‐band optimizes the electronic configuration. The Cu‐substrate enables the surface Ni–Mo alloy dots to be more electron‐rich, forming a local connected electron‐rich network, which boosts the charge transfer for effective binding of O‐related species and proton–electron charge exchange in the hydrogen evolution reaction. The Cu‐supported Ni₄Mo/MoO_x shows an ultralow overpotential of 16 mV at a current density of 10 mA cm^?2 in 1 m KOH, demonstrating the smallest overpotential, at loadings as low as 0.27 mg cm^?2, among all non‐noble metal catalysts reported to date. Moreover, an overpotential of 105 mV allows it to achieve a current density of 250 mA cm^?2 in 70 °C 30% KOH, a remarkable performance for alkaline hydrogen evolution with competitive potential for applications.     

Characterization of the A in equilibrium B transition of DNA in fibers and gels by laser Raman spectroscopy.

Both Raman spectra and X-ray diffraction patterns have been obtained from oriented fibers of sodium deoxyribonucleic acid (Na-DNA) as a function of salt content and relative humidity. We have confirmed the previously reported X-ray results that, for oriented fibers, the A-form always exists between 75 and 92% relative humidity and that the conformation will change to the B-form at 92% relative humidity only if an excess (3–5%) of added salt is present. Oriented fibers containing low amounts of added salt remain in the A-type conformation at 92% relative humidity and higher. An exact correlation has been found between the familiar A- and B-type X-ray diffraction patterns of DNA fibers and the Raman spectra previously reported without X-ray verification from this laboratory for the A- and B-forms. In particular, a band at 807 cm^?1 was always present when a fiber showed the A-type diffraction pattern, and this band shifts to 790 cm^?1 in the B-form. Using the Raman spectrum to determine the specific conformation of DNA in samples less amenable to X-ray analysis, we have studied the A ? Btransformation in unoriented fibrous masses of DNA and in concentrated, oriented gels. We find that in unoriented fibrous masses, the A ? B transition always occurs at 92% relative humidity even at very low salt concentration (0–4%). However, in oriented DNA gels at low salt, the A-form can persist as a metastable state to concentration as low as 20% DNA. The origin of the bands at 807 and 790 cm^?1 and the possible biological implications of these findings are discussed.     

An FT-IR Study of DNA and RNA Conformational Transitions at Low Temperatures

Abstract

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.     

Complex biopolymeric systems at stalk/epicuticular wax plant interfaces: A near infrared spectroscopy study of the sugarcane example

Naturally occurring macromolecules present at the epicuticular wax/stalk tissue interface of sugarcane were investigated using near infrared spectroscopy (NIRS). Investigations of water, cellulose, and wax‐cellulose interrelationships were possible using NIRS methods, where in the past many different techniques have been required. The sugarcane complex interface was used as an example of typical phenomena found at plant leaf/stalk interfaces. This detailed study showed that sugarcane cultivars exhibit spectral differences in the CH_n, water OH, and cellulose OH regions, reflecting the presence of epicuticular wax, epidermis, and ground tissue. Spectrally complex water bands (5276 cm^?1 and 7500–6000 cm^?1) were investigated via freeze‐drying experiments which revealed sequentially a complex band substructure (7500–6000 cm^?1), a developing weak H‐bonding system (～7301 cm^?1), and strong H‐bonding (～7062 cm^?1) assigned to water—cellulose interactions. Principal component analysis techniques clarified complex band trends that developed during the desorption experiment. Bands from wax‐free stalk were minimized in the 4327–4080 cm^?1 region (C? H_n vibrational modes associated with long chain fatty compounds), while bands from the stalk tissue (particularly lignin and moisture) became more pronounced. This work is a comprehensive guide to similar studies by scientists involved in a variety of plant and fiber research fields. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 642–651, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Raman spectroscopic analysis of the sodium salt of kappa-carrageenan and related compounds in solution

Laser-Raman spectra of Na⁺ kappa-carrageenan, Na⁺ neocarrabiose 4-sulphate, and neocarrabiose in the region 700–1500 cm⁻¹ are reported for solutions in H₂O and D₂O. The C-1-H-1α vibration, coupled with COH related modes, is assigned to a band at 840 cm⁻¹, close to the maximum of the symmetrical COS stretching (∼850 cm⁻¹). The symmetrical SO stretch is proposed to occur near 1040 cm⁻¹ and is probably coupled with COH vibrations which give rise to strong bands in the region 1000–1100 cm⁻¹. The intense band in the region 730–740 cm⁻¹ is ascribed to a complex ring vibration.     

A resonance Raman study on the interaction of rifampicin with Escherichia coli RNA polymerase

The technique of resonance Raman spectroscopy has been used to investigate the interaction of the antibiotic rifampicin with Escherichia coli RNA polymerase. Spectra were analyzed by generating the first derivative of each recorded spectrum using the Savitsky-Golay algorithm. The only band that shifted significantly in the resonance Raman spectrum of rifampicin upon the formation of the drug-core polymerase complex was the amide III band. It underwent an 8 cm^?1 shift from 1306 cm^?1 in aqueous solution to 1314 cm^?1. A comparable shift was observed for the rifampicin-holoenzyme complex. Thus, the interaction of the sigma subunit with the core polymerase does not significantly alter the manner in which rifampicin interacts with RNA polymerase. The nature of this shift has been analyzed further by recording the resonance Raman spectrum of rifampicin in a variety of solvents with different hydrogen-bonding ability. In non-hydrogen-bonding solvents (benzene and carbon disulfide) the amide III band was observed at approximately 1220 cm^?1; in dimethyl sulfoxide, a weak hydrogen-bond acceptor, 1274 cm^?1; in water, a strong hydrogen-bonding solvent, 1306 cm^?1; and finally, in triethylamine, a stronger hydrogen-bonding solvent than water, it was observed at 1314 cm^?1. Thus, as the hydrogen-bonding ability of the solvent increased, the amide III band shifted to higher frequency. Based on these results, the rifampicin binding site in RNA polymerase provides a stronger hydrogen-bonding environment for the amidic proton of rifampicin than is encountered when rifampicin is free in aqueous solution.     

Resonance Raman spectra of mononucleotides obtained with 266 and 213 nm ultraviolet radiation

Resonance Raman spectra of the nucleoside 5′-monophosphates UMP, CMP, AMP, and GMP have been obtained with 266- and 213-nm radiation, the fourth and fifth harmonics of a Nd:YAG laser. The 266-nm radiation is resonant with the states giving rise to the first absorption band of the bases. The resulting spectra are in agreement with those reported previously using similar wavelength excitation but are generally of better quality. The 213-nm radiation is resonant with those states giving rise to the second strong absorption band of the bases. The spectra obtained with this wavelength show several new features relative to the 266-nm spectra, including strong enhancement of modes of the pyrimidines with a character similar to the e_2g ν₈ mode of benzene, relative enhancement of ring modes at 1580 and 729 cm^?1 in AMP, and strong enhancement of the 1670-cm^?1 C = O mode of GMP. These enhancements are discussed in terms of previously reported preresonance behavior and predicted intensities based on CNDO bond-order changes and normal-mode calculations. The results of a preliminary study of the effect of the interaction of GMP with cis-dichlorodiammineplatinum(II) on the 213-nm resonance Raman spectrum is also discussed.