SynopsisThe ltaman spectra of collagen, gelatin, and elastin are presented. The Raman lines in the latter two spectra are assigned by deuterating the amide N-H groups in gelatin and by studying the superposition spectra of the constituent amino acids. Two lines appear a t 1271 and 1248 cm-1 in the spectra of collagen and gelatin that can be assigned to the amide I11 mode. Possibly, the appearance of two amide I11 lines is related to the biphasic nature of the tropocollagen molecule, i.e., proline-rich (nonpolar) and proline-poor (polar) regions distributed along the chain. The melting, or collagen-togelatin transition, in water-soluble calf skin collagen is studied and the 1248-cm-I amide I11 line is assigned to the 31 helical regions of the tropocollagen molecule.Elastin is thought to be mostly random and the Itaman spectrum confirms this assertion. Strong amide I and I11 lines appear a t 1668 and 1254 cm-', respectively, and only weak scattering is observed a t 938 cm-1. These features have been shown to be characteristic of the disordered conformation in proteins.

synopsisRaman spectroscopy has been used in investigating the conformational transitions of poly-calanine (PLA) induced by mechanical deformation. We see evidence of the alpha-helical, antiparallel beta-sheet, and a disordered conformation in PLA. The disordered conformation has not been discussed in previous infrared and X-ray diffraction investigations and may have local order similar to the left-handed 31 polyglycine helix. The amide I11 mode in the Raman spectrum of PLA is more sensitive than the amide I and I1 modes to changes in secondary structure of the polypeptide chain. Several lines below 1200 cm-1 are conformationally sensitive and may generally be useful in the analysis of Raman spectra of proteins. A line at 909 cm-1 decreases in intensity after deformation of PLA. In general only weak scattering is observed around 900 cm-1 in the Raman spectra of antiparallel beta-sheet polypeptides.The Raman spectra of the amide N-H deuterated PLA and poly-cleucine (PLL) in the alpha-helical conformation and poly-cvaline (PLV) in the beta-sheet conformation are presented. Splitting is observed in the amide I11 mode of PLV and the components of this mode are assigned. The Raman spectrum of an alpha-helical random copolymer of L-leucine and bglutamic acid is shown to be consistent with the spectra of other alphahelical polypeptides.

SynopsisThe conformational transitions in water and in the solid state of poly-bglutamic acid (PGA) and poly-bornithine (PO) have been studied by Raman spectroscopy. The Raman spectra of PGA, PO, and the monomer, dimer, and trimer of PGA in aqueous solutions and solid state are presented. The Raman spectral changes of PGA and PO were followed through the helix-to-coil transition induced by pH, temperature, and solvent composition. A hyperchromic shift in the intensity of the amide 111 line accompanying the helix-to-coil transition was observed. This hyperchromic intensity shift occurs abruptly as a function of pH but more slowly with heat denaturation of the alpha helix indicating that the Raman spectrum is sensitive to the transition mechanism. The high-temperature coil and the charged coil may have different conformations as evidenced by different amide I11 frequencies but similar intensities in these two conformations.

The article contains sections titled: 1. Polystyrene 1.1. Introduction 1.2. Production 1.2.1. Bulk Polymerization 1.2.2. Suspension Polymerization 1.3. Properties 1.3.1. Chemical Properties 1.3.2. Physical and Processing Properties 1.4. Processing and Uses 1.5. Quality Specifications 1.6. Storage and Transportation 1.7. Recycling 1.8. Environmental Aspects 2. Styrene – Acrylonitrile (SAN) Copolymers 2.1. Production 2.2. Properties 2.3. Processing 2.4. Uses and Economic Aspects 2.5. Blending of SAN 3. Barrier Resins 4. Other Copolymers 4.1. α‐Methylstyrene – Acrylonitrile Copolymers 4.2. Styrene – Methyl Methacrylate Copolymers 4.3. Styrene – Maleic Anhydride Copolymers 4.4. Styrene – Maleimide Copolymers 4.5. Styrene – Acrylate Copolymers 5. Acrylonitrile – Butadiene – Styrene (ABS) Polymers 5.1. Definition and Structure 5.1.1. Historical Aspects 5.1.2. Structural Principles 5.1.3. Synthesis of the Two‐Phase Structure 5.1.4. Properties of the Resin Matrix 5.2. Structure – Property Relationships 5.3. Production of ABS Polymers 5.3.1. ABS Production by Emulsion Polymerization 5.3.2. Production of the Matrix Copolymer 5.3.3. ABS Production by Bulk Polymerization 5.3.4. Process Combinations 5.3.5. Other Processes 5.3.6. Additives 5.4. Quality Assurance and Standardization 5.5. Properties 5.6. Special Product Modifications 5.7. Legal Aspects 5.8. Storage and Transportation 5.9. Uses 5.10. Economic Aspects 5.11. Recycling 5.12. ABS‐Analogous Systems 5.12.1. ASA, AES, and ACS Polymers 5.12.2. MBS and MABS Polymers 5.13. ABS Blends

SynopsisRaman spectra of the pH denaturation of tropomyosin are presented. In the native state tropomyosin has an alpha-helical content of nearly 90%, but this value drops rapidly as the pH is raised above 9.5. The Raman spectrum of the native state is characterized by a strong amide I line appearing a t 1655 cm-1, very weak scattering in the amide I11 region around 1250 cm-1, and a medium-intensity line a t 940 cm-1. When the protein is pH-denatured, a strong amide I11 line appears a t 1254 cm-l and the 940 cm-l line becomes weak. The intensities of the latter two lines are a sensitive measure of the alpha-helical and disordered chain content. These results are consistent with the helixto-coil studies of the polypeptides.The Raman spectra of a-casein and prothrombin, proteins thought to have little or no ordered secondary structure, are investigated. The amide I11 regions of both spectra display strong lines a t 1254 cm-1 and only weak scattering is observed a t 940 cm-l, features characteristic of the denatured tropomyosin spectrum. The amide I mode of acasein appears a t 1668 cm-1, in agreement with the previously reported spectra of disordered polypeptides, poly-cglutamic acid and poly-Llysine a t pH 7.0 and mechanically deformed poly-Lalanine. 1809