Triapine (3-aminopyridine-2-carboxaldehyde- thiosemicarbazone): A potent inhibitor of ribonucleotide reductase activity with broad spectrum antitumor activity.

Previous studies from our laboratories have shown that (a) Triapine() is a potent inhibitor of ribonucleotide reductase activity and (b) hydroxyurea-resistant L1210 leukemia cells are fully sensitive to Triapine. In an analogous manner, Triapine was similarly active against the wild-type and a hydroxyurea-resistant subline of the human KB nasopharyngeal carcinoma. Triapine was active in vivo against the L1210 leukemia over a broad range of dosages and was curative for some mice. This agent also caused pronounced inhibition of the growth of the murine M109 lung carcinoma and human A2780 ovarian carcinoma xenografts in mice. Optimum anticancer activity required twice daily dosing due to the duration of inhibition of DNA synthesis which lasted about 10 hr in L1210 cells treated with Triapine in vivo. DNA synthesis in normal mouse tissues (i.e. duodenum and bone marrow) uniformly recovered faster than that in L1210 leukemia cells, demonstrating a pharmacological basis for the therapeutic index of this agent. Triapine was more potent than hydroxyurea in inhibiting DNA synthesis in L1210 cells in vivo, and the effects of Triapine were more pronounced. In addition, the duration of the inhibition of DNA synthesis in leukemia cells from mice treated with Triapine was considerably longer than in those from animals treated with hydroxyurea. Combination of Triapine with various classes of agents that damage DNA (e.g. etoposide, cisplatin, doxorubicin, and 1-acetyl-1,2-bis(methylsulfonyl)-2-(2-chloroethyl)hydrazine) resulted in synergistic inhibition of the L1210 leukemia, producing long-term survivors of tumor-bearing mice treated with several dosage levels of the combinations, whereas no enhancement of survival was found when Triapine was combined with gemcitabine or cytosine arabinoside. The findings demonstrate the superiority of Triapine over hydroxyurea as an anticancer agent and further suggest that prevention by Triapine of repair of DNA lesions created by agents that damage DNA may result in efficacious drug combinations for the treatment of cancer.

Hypoxia-selective nitrobenzyloxycarbonyl derivatives of 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazines.

Some 4- and 2-(nitrobenzyloxycarbonyl)-1, 2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazines (4, 6, and 7) were synthesized and evaluated for their ability to exert preferential toxicity to hypoxic EMT6 mammary carcinoma cells using a colony-forming assay. Of these, the 4,5-dimethoxy-2-nitro analogue 6 (50 microM, 1-h exposure) caused greater than 3 logs of kill of hypoxic cells, with relatively minor toxicity to corresponding aerobic cells. The ability of 4-nitro (4) and 4,5-dimethoxy-2-nitro (6) analogues to reach and kill hypoxic cells of solid tumors was also demonstrated using intradermally implanted EMT6 solid tumors in mice. In addition, a possible source of toxicity to normal tissue, i. e., the activation of the 4-nitrobenzyl derivative 4 by glutathione S-transferase-catalyzed thiolysis, was essentially eliminated by replacing one of the benzylic methylene protons by a methyl group. The 4-nitro (4) and 4,5-dimethoxy-2-nitro (6) analogues also appear to be reduced more easily under acidic conditions (pH 6.0) than under neutral conditions, as measured by differential pulse polarography. Since the pH in hypoxic regions is often lower than that in adjacent aerobic regions, this property should aid in the cytotoxic action of these agents against hypoxic cells of solid tumors.

OH-H2 entrance channel complexes.

The entrance channel to the OH+H2-->H2O+H hydrogen abstraction reaction has been investigated from several different experimental approaches and complementary theoretical calculations. Weakly bound complexes between the hydroxyl radical and molecular hydrogen have been stabilized within a shallow well in the entrance channel and characterized via electronic spectroscopy on the OH A2Sigma+-X2Pi transition. Laser-induced fluorescence and fluorescence depletion experiments have revealed the binding energy of H2/D2 with ground state OH X2Pi radicals, the intermolecular energy levels supported by the OH A2Sigma+ (v'=0,1)+H2/D2 potential, and the OH-H2/D2 excited state dissociation limit. The OH X2Pi + H2 potentials have also been examined through inelastic scattering measurements on Lambda-doublet state-selected OH with normal or para-H2. Finally, photodetachment of an electron from the H3O- anion enabled the neutral reaction to be probed in conformations sampled by the two isomeric forms of the anion.

Antitumor 2-(aminocarbonyl)-1,2-bis(methylsulfonyl)-1-(2-chloroethyl)- hydrazines.

Several 2-(aminocarbonyl)-1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydr azi nes were synthesized and primarily evaluated for antitumor activity against the murine L1210 leukemia. All of the compounds tested were capable of producing "cures" of mice bearing this tumor. One of the most active agents of this class, 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)- 2(-)[[2-chloroethyl)-amino]carbonyl]hydrazine, was further evaluated against a spectrum of transplanted murine and human solid tumors. Pronounced activity was found against all of the tumors including the murine B16F10 melanoma, M109 lung carcinoma, M5076 reticulum cell sarcoma, and the human LX-1 lung carcinoma. The activities observed compared favorably with those of the established antitumor drugs, cyclophosphamide, mitomycin C, and the nitrosoureas, evaluated concomitantly.

Synthesis and evaluation of 1-acyl-1,2-bis(methylsulfonyl)-2-(2- chloroethyl)hydrazines as antineoplastic agents.

A series of 1-acyl-1,2-bis(methylsulfonyl)-2-(2-chloroethyl)hydrazines, conceived as more potent analogs of 1-(2-chloroethyl)-1,2,2-tris(methylsulfonyl)hydrazine, were synthesized and evaluated for antineoplastic activity against the L1210 leukemia in mice. Of these, 1-acetyl-1,2-bis-(methylsulfonyl)-2-(2-chloroethyl)hydrazine produced "cures" of mice bearing the L1210 leukemia at dosage levels that were considerably less than those at which the tris(sulfonyl) analog produced its antineoplastic effects. This compound was also found to have pronounced activity against the P388 leukemia and against several solid tumors, including the B16F10 melanoma, the M5076 reticulum cell sarcoma, and the M109 lung carcinoma. Furthermore, the acyl derivatives were in general considerably more resistant to hydrolysis in aqueous media and more prone to protease- and thiol-mediated activation than the tris(sulfonyl) analog. The former property is important to formulation, while the latter properties may result in some degree of drug targeting and enhancement of the therapeutic indices of these agents.

Solution and solid-state circular dichroism analyses of a human salivary proline-rich glycoprotein repeating domain and its subfragments.

Solution- and solid-state c.d. spectra, as well as surface energetics values, were collected for a series of peptides derived from human salivary proline-rich glycoprotein (PRG). The acronyms and sequences for these peptides are as follows: PRG9-2 = NH2-G(1)-P(2)-CONH2, PRG9-3 = NH2-G(1)-P(2)-P(3)-CONH2, PRG9-4 = NH2-G(1)-P(2)-P(3)-P(4)-CONH2, PRG9-5 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-CONH2, PRG9-6 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-CONH2, PRG9-7 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-CONH2, PRG9-8 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-CONH2, and PRG9-9 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-P(9)-CONH2. The presence of stable poly-L-proline II-like 'mini' helices in the solution state was found to be dependent on peptide chain length, pH, salt, and organic solvent type. Other conformational features such as kinks and beta-/gamma-turns were also found in the larger peptides. Solid-state peptide conformations were not necessarily related to their solution-state counterparts. Poly-L-proline II-like 'mini' helices, kinks, and beta-/gamma-turns were similarly found in the various substrate-bound PRG9 peptides. Surface energetics parameters suggested specific orientations for PRG9 peptides and their constituent acids and homopolymers.

Comparative biophysical study of adsorbed calf serum, fetal bovine serum and mussel adhesive protein films.

Varying concentrations of different sera and adhesive agents are routinely used to increase cellular attachment to substrata. The surface-chemical effects of some of these surface-altering materials have been examined using ellipsometry, contact angle analysis and multiple-attenuated internal reflection infrared (MAIR-IR) spectroscopy. Specifically, 15% fetal bovine serum (FBS), Ham's F-12 (containing 10% FBS + 1% penicillin/streptomycin), 10% calf serum and mussel adhesive protein (MAP) were allowed to adsorb on to similar and different surfaces and then compared. Each of these preparations is capable of altering the surface-chemical properties of substrata with varying resultant surface energies. It is therefore important to characterize serum in the proper concentrations on the substrata under consideration in order to understand the interfacial effects.

Surface properties of mussel adhesive protein component films.

Mussel adhesive protein (MAP) is the adhesive agent used by the blue sea mussel (Mytilus edulis) to attach the animal to various underwater surfaces. It is composed of 75-->85 repeating decameric units with the reported primary sequence NH2-A(1)-K(2)-P(3)-S(4)-Y(5)-Hyp(6)-Hyp(7)-T(8)-DOPA(9)-K(10)-COOH. This study identifies and compares the surface properties of the decameric unit, selected fragments and individual amino acid constituents with the complete MAP preparation. These molecular systems were examined: (a) in the solid state as thin films formed on germanium substrata using multiple-attenuated-internal-reflectance infrared (MAIR-IR) spectroscopy, ellipsometry and contact angle analysis; and (b) in the solution state using circular dichroism (CD) spectroscopy. Extensive molecular modelling of the decamer was performed making integral use of the experimentally derived data. These cumulative semi-empirical and empirical results suggest a conformation for the decamer that closely associates the L-DOPA and tyrosine residues with the solid substratum. This model provides the first representation of MAP derived from a rational integration of theoretical and experimental data. On the basis of this model, a possible explanation for the bioadhesive properties of MAP is suggested.

Investigation of cis/trans proline isomerism in a multiply occurring peptide fragment from human salivary proline-rich glycoprotein.

The solution-state conformations of eight proline-containing peptide fragments found in human salivary proline-rich glycoprotein (PRG) were investigated in 2 x distilled water (treated with metal ion chelating resin) using 13C-nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopy. The peptide sequences and acronyms were as follows: PRG9-2 = NH2-G(1)-P(2)-CONH2, PRG9-3 = NH2-G(1)P(2)-P(3)-CONH2, PRG9-4 = NH2-G(1)-P(2)-P(3)-P(4)-CONH2, PRG9-5 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-CONH2, PRG9-6 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-CONH2, PRG9-7 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-CONH2, PRG9-8 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-CONH2 and PRG9-9 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-P(9)-CONH2. Sequence-specific resonance assignments from the 13C-NMR spectra indicated that the trans proline isomer dominated the conformations of the peptides. CD results clearly showed the presence of the poly-L-proline II helix as the major conformation in PRG9-3----PRG9-5, supplemented by beta- and/or gamma-turns in PRG9-6----PRG9-9. These data suggest that in "metal free" water, native PRG could contain several small poly-L-proline II helices along with beta- and/or gamma-turns. Since proline is the major amino acid present in native PRG, these localized conformations may contribute to PRG's global conformation and act as a primary force in determining its biological activities.

Activity of C-7 substituted cyclic acetal derivatives of mitomycin C and porfiromycin against hypoxic and oxygenated EMT6 carcinoma cells in vitro and in vivo.

A series of cyclic acetal derivatives of mitomycin C (MC) and porfiromycin (POR) were tested for their ability to kill hypoxic and oxygenated EMT6 tumor cells. Amino methyl acetal and thioacetal substitutions at C-7 of MC and POR dramatically increased the cytotoxicity of the compounds to hypoxic EMT6 tumor cells in vitro but had little effect on the aerobic toxicities. In contrast, a methyl substitution at N1a markedly decreased the aerobic cytotoxicities of the compounds but did not alter the hypoxic cytotoxicities. The POR acetal, BMY-42355, had the largest differential between hypoxic and aerobic cytotoxicities yet observed among MC analogs. Preliminary studies in mice showed that BMY-42355 had good antineoplastic activity when used alone or in combination with radiation and was less toxic than POR; the therapeutic ratio of this compound in these initial studies was higher than those of either MC or POR.

Cytotoxicity and DNA crosslinks produced by mitomycin analogs in aerobic and hypoxic EMT6 cells.

Several mitomycin antibiotics were evaluated for their capacities to kill EMT6 tumor cells and to produce DNA crosslinks under conditions of oxygenation and hypoxia. The agents examined included mitomycin C, porfiromycin, and the 7-aminomethyl dithioacetal derivative of mitomycin C (BMY-43324), all of which caused greater kill of hypoxic cells than of their oxygenated counterparts; the N,N'-dimethylaminomethylene derivative of mitomycin C (BMY-25282), which was considerably more cytotoxic under oxygenated conditions than in hypoxia; and the N,N'-dimethylaminomethylene derivative of porfiromycin (BL-6783), which was equal in its toxicity to hypoxic and oxygenated cells. All of these agents produced DNA crosslinks in EMT6 cells, as measured by alkaline elution. The number of crosslinks required to produce a given amount of cell kill was similar, regardless of the mitomycin employed or the degree of oxygenation, suggesting that the crosslinking of DNA was a major lesion in the cytodestructive action of the mitomycins.

Synthesis and evaluation of 1,2,2-tris(sulfonyl)hydrazines as antineoplastic and trypanocidal agents.

Several 1,2,2-tris(sulfonyl)hydrazines, conceived as prodrugs of 1,2-bis(sulfonyl)hydrazines, were synthesized and evaluated for antineoplastic and trypanocidal activities in mice. 1-Methyl-1,2,2-tris(methylsulfonyl)hydrazine emerged as an extremely efficacious antitrypanosomal agent, whereas 1-(2-chloroethyl)-1,2,2-tris(methylsulfonyl)hydrazine was inactive. In contrast, 1-(2-chloroethyl)-1,2,2-tris(methylsulfonyl)hydrazine displayed potent antineoplastic activity, producing several 60-day "cures" of mice bearing leukemia L1210, leukemia P388, or Sarcoma 180. Furthermore, the fact that the tris(sulfonyl) derivatives will not generate isocyanates, which contribute to the host toxicity of nitrosoureas like 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), makes them agents of significant promise in trypanosomal and cancer chemotherapy.

N.m.r. analyses of the histidine microenvironments in a human salivary proline-rich glycoprotein.

The pKa's of the three histidine residues in a proline-rich glycoprotein from human parotid saliva (PRG) were determined by 360 MHz proton n.m.r. spectroscopy. The addition of calcium (0.64 mM) caused drops in the pKa's of all three histidines by approximately 0.25 units. When imidazole and cyclo)L-histidine-L-proline) were used as model compounds, corresponding concentrations of calcium had no effect on their pKa's. Also, the model compounds gave absolute pKa values in good agreement with similar chemical species reported in the literature. Exchange lifetime data and previously reported hydrogen----deuterium exchange experiments suggest that the PRG histidine N tau H protons are not involved in hydrogen-bonds. Collectively, these data imply that changes in PRG conformation occur upon the addition of calcium.

N.m.r. and computer-simulated conformational analyses of a nonapeptide found in a human salivary proline-rich glycoprotein.

The amino acid sequence G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-P(9) occurs twice in the proline-rich glycoprotein (PRG) found in human parotid saliva. As part of our efforts to elucidate the structure-function relationships of PRG, this nonapeptide sequence (PRG9) was synthesized for the purpose of conformational analyses by high-resolution proton n.m.r. spectroscopy and computer-modeling. The empirical n.m.r. spectrum differed from the simulated spectrum in that the overall chemical shift locations were displaced from their random coil positions and the five proline residues had non-degenerate C alpha H alpha protons. Other n.m.r. data indicated that no intramolecular hydrogen-bonding was present in the PRG. In conjunction with X-ray crystallographic data on a triproline-containing model compound (Kartha, g., Ashida, T. & Kakudo, M. (1974) Acta Cryst. B30, 1861-1866), four energy-minimized PRG9 structures were obtained. Two of the structures were energetically unfavorable, while the other two conformations were reasonable. The two most likely structures gave all prolines an S-type ring pucker, the P(2)-P(3)-P(4) sequence as a poly-L-proline II helix, the H(5) phi = -90.3 degrees, P(6) and P(9) with trans peptide bond orientation, G(7) in an extended state, and the K(8) phi = -93.2 degrees or -146.8 degrees for structures #1 and #2, respectively.

Individual differences in auditory electric responses: comparisons of between-subject and within-subject variability. II. Amplitude of brainstem Vertex-positive peaks.

Recently, we (Lauter & Loomis, 1986) reported variability measures of the latency of five vertex-positive auditory brainstem response (ABR) peaks collected under a repeated-measures experimental design. Seven subjects were tested, each on eight separate sessions, for brainstem auditory evoked response to monaural right, monaural left, and binaural stimulus presentation. This paper presents variability measures for amplitudes of the same series of responses. Three types of variability measurement were made: 1) amplitude of each peak of the response to monaural right, monaural left, and binaural stimulation; 2) amplitude difference for each peak comparing binaural with right, and binaural with left; and 3) amplitude difference comparing binaural with the sum of the amplitudes of the two monaural responses. As in the previous report, between-subject variability and within-subject variability were expressed using a ratio of mean divided by standard deviation (this is the reciprocal of Pearson's Coefficient of Variation, and will here be referred to as the Coefficient of Stability, or Cs). For all amplitude comparisons, Cs profiles indicate that: 1) within-subject stability (i.e., consistency) is significantly greater than between-subject stability, 2) both within- and between-subject stability measures are sensitive to both peak and ear of presentation, and 3) stability profiles for individual subjects show individual differences and similarities, and are replicable over time. The variability measure also provides evidence of an ear asymmetry at peak III which has been noted in other ABR studies.

Biochemical and biophysical comparison of two mucins from human submandibular-sublingual saliva.

A high-molecular-weight mucin-glycoprotein (MG1) was isolated from human submandibular-sublingual saliva and was comprised of 14.9% protein, 29.0% N-acetylglucosamine, 9.4% N-acetylgalactosamine, 10.5% fucose, 24.2% galactose, 0.9% mannose, 4.0% N-acetylneuraminic acid, and 7.0% sulfate. Carbohydrate units were O-glycosidically linked and ranged in size from 4 to 16 residues. The biophysical properties of MG1 were compared to those of a smaller mucin (MG2) also isolated from submandibular-sublingual saliva. Fluorescence spectroscopy demonstrated that MG1 bound both 1-anilino-8-naphthalenesulfonate (ANS) and N-phenyl-1-naphthylamine (NPNA) in stable hydrophobic binding sites (melting temperature, 47 +/- 2 degrees C), whereas MG2 did not bind these hydrophobic probes. These hydrophobic domains occurred on nonglycosylated or naked portions of MG1 since Pronase treatment eliminated ANS binding. Reduction of disulfide bridges in MG1 increased the number of available hydrophobic binding sites. High ionic strength (0 to 2 M NaCl) had no effect on ligand binding, whereas lowering pH (9 to 2) increased ANS binding without affecting NPNA complexation. Circular dichroism (CD) data suggested that MG1's carbohydrate chains dominated its spectrum. In contrast, the peptide backbone dominated the CD spectrum of MG2. Collectively, the results of this study indicate that human submandibular-sublingual saliva contains two structurally distinct mucins.

Cell-mediated amplification and down regulation of cytotoxic immune response against autologous human cancer.

The cytotoxic host immune response toward autologous human cancer may be regulated by the immunoregulatory network. Here we show that helper T cells, cloned from peripheral blood lymphocytes that were sensitized in vitro against an autologous human malignant paraganglioma, proliferated against and made interleukin 2 when cocultured with the tumor-associated antigen in the presence of autologous accessory cells. Furthermore, the helper cell clones amplified cytotoxic immune response by peripheral blood lymphocytes against the paraganglioma cells in coculture with the blood lymphocytes and the paraganglioma cells. An autologous T cell line bearing suppressor phenotype, established from a lymph node that had been infiltrated with the paraganglioma tumor cells, in contrast to the helper cells, selectively suppressed the cytotoxic immune response by the blood lymphocytes against the paraganglioma cells in identical coculture. These results, therefore, demonstrate the existence of cell-mediated immunologic regulations of the cytotoxic immune response (concurrent amplification and suppression in the same host) against an autologous human tumor.

Nuclear magnetic resonance spectroscopic and computer-stimulated structural analyses of a heptapeptide sequence found around the N-glycosylation site of a proline-rich glycoprotein from human parotid saliva.

The proline-rich glycoprotein from human parotid saliva has a common heptapeptide sequence around four of six N-glycosylation sites (Maeda, N., H. S. Kim, E. A. Azen, and O. J. Smithies, 1985, J. Biol. Chem., 20:11123-11130). A synthetic model of the heptamer protein sequence, NH2-Q(1)-G(2)-G(3)-N(4)-Q(5)-S(6)-Q(7)-CONH2, was examined by nuclear magnetic resonance (NMR) spectroscopy and the ECEPP/2-VAO4A (Empirical Conformation Energy Program for Peptides) energy minimization computer algorithm (Scheraga, H. A., 1982, Quantum Chemistry Program Exchange, 454; Powell, M. J. D., 1964, Quantum Chemistry Program Exchange, 60). The NMR spectrum was almost completely assigned in dimethylsulfoxide-d6 (DMSO), and the amide chemical shift temperature dependence, phi dihedral angles, and chi 1 rotamer populations elucidated. These data indicated that a significant population of the heptamer could exist as a type I beta-turn [4----1 between Q(5) and G(2)] and/or a type II' beta-turn [4----1 between (Q)5 and G(2) and/or a gamma-turn [3----1 between Q(5) and G(3)] with the amino acid chi 1 torsion angles weighted toward the gauche- conformation. Starting from these three possible conformations, the ECEPP/2-VAO4A rigid geometry energy minimization program was used to find the localized predominant in vacuo structures of this heptapeptide sequence. The type II' beta-turn conformation best fits the data based on internuclear hydrogen-bonding distances, minimum potential energy considerations, and the NMR parameters.

Structural aspects of salivary glycoproteins.

The protective functions of saliva are attributed, in part, to its serous and mucous glycoproteins. We have studied, as representative molecules, the proline-rich glycoprotein (PRG) from human parotid saliva and the high (MG1) and low (MG2) molecular weight mucins from submandibular-sublingual saliva. PRG (38.9 kDa) contains 40% carbohydrate consisting of 6 triantennary N-linked units and a single peptide chain of 231 amino acids, 75% of which = PRO + GLY + GLN. PRG's secondary structure is comprised of 70% random coil (naked regions) and 30% beta-turns (glycosylated domains). MG1 (greater than 10(3) kDa) contains 15% protein (several disulfide linked subunits), 78% carbohydrate (290 units of 4-16 residues), 7% sulfate, and small amounts of covalently linked fatty acids. MG2 (200-250 kDa) contains 30% protein (single peptide chain), 68% carbohydrate (170 units of 2-7 residues), and 2% sulfate. The major carbohydrate units of MG2 are: NeuAc alpha 2,3Gal beta 1,3GalNAc,Gal beta 1,3GalNAc, and Fuc alpha 1,2Gal beta 1,3GalNAc. MG1 contains hydrophobic domains, as evidenced by its ability to bind fluorescent hydrophobic probes; MG2 does not. Collectively, the biochemical and biophysical comparisons between MG1 and MG2 indicate that these two mucins are structurally different. Several functional properties of MG1, MG2, and PRG have been examined, including their presence in two-hour in vivo enamel pellicle, binding to synthetic hydroxyapatite, lubricating properties, and interactions with oral streptococci. The data presented suggest that these glycoproteins may have multiple functions which are predicated, in part on their carbohydrate units. The potential significance of the structure-function relationships of these glycoproteins to the oral ecology is discussed.