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E Kay

Publications and source records attributed to E Kay.

At least 73 records · Page 4Linked to original sources
PubMed1988

A sense of style.

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Dental Offices↗
PubMed1982

Assembly of the fertilization membrane of the sea urchin: isolation of a divalent cation-dependent intermediate and its crosslinking in vitro.

To analyze the mechanism of assembly of the fertilization membrane of the sea urchin Strongylocentrotus purpuratus, we inhibited the ovoperoxidase that catalyzes dityrosine formation to isolate an uncrosslinked, soft fertilization membrane (SFM). The SFM intermediates were stabilized by divalent cation-dependent interactions: in the absence of divalent cations, the SFM became amorphous and less refractile and released proteins into the surrounding medium. We term the remaining structures "wraiths." The rate of this disaggregation was increased in solutions of low ionic strength, but 5-10 mM divalent cations (Ca2+, Mg2+, Mn2+ or Ba2+) prevented disaggregation. Wraiths could be reassembled into structures that resembled SFM by readdition of divalent cations. The SFM contained active ovoperoxidase and could be hardened in vitro by washing away the ovoperoxidase inhibitor and adding H2O2. After hardening, certain proteins of over 100 kd were excluded from SDS-polyacrylamide gels, suggesting that these proteins contain the substrates for crosslinking. We propose that the SFM is a divalent cation-dependent intermediate on the pathway of fertilization membrane assembly containing tyrosyl residues that are appropriately juxtaposed for crosslinking.

Calcium↗
PubMed1979

Lima bean proteinase inhibitor. Origins of circular dichroism bands and modification by Br2- and (CNS)2-.

Origins of CD bands in lima bean proteinase inhibitor were deduced from an acetylation-deacetylation study of the sole tyrosyl residue in the protein (Tyr 69), and by analogy with Bowman-Birk soybean proteinase inhibitor, a homologous protein with similar spectral properties. Tyr 69 is relatively inaccessible to N-acetylimidazole; 100-fold molar excess of the reagent in the presence of 6 M guanidine hydrochloride elicited about 70 to 80% O-acetylation. A broad negative CD band centered around 280 nm arises mainly from the longest wavelength transition of cystinyl side chains (epsilon L--epsilon R approximately equal to -0.8 M-1 cm-1 per disulfide). The second cystinyl transition gives rise to a positive CD band of a comparable intensity at 247 nm. The Lb vibronic transition of Tyr 69 has negative CD around 280 nm, contributing approximately 10% of the total CD intensity at 278 nm (epsilon L--epsilon R approximately equal to -0.5 M-1 cm-1). The 232 nm positive shoulder is from the La vibronic transition of Tyr 69. Radical anions, Br2- and (CNS)2-, generated by the irradiation of N2O-saturated inhibitor solutions containing KBr or KCNS, reduced tyrosyl CD without affecting disulfide CD bands, indicating that the radical anions damaged Tyr 69 without altering protein conformation. The inhibitor modified at Tyr 69 by Br2- and (CNS)2- retained full activity toward trypsin and chymotrypsin. The irradiation of the inhibitor in the air-saturated solution led to loss in tyrosyl as well as cystinyl CD bands and decline in both antiproteinase activities.

Bromides↗
PubMed1979

Differences in the circular dichroism spectra of of eu- and heterochromatin fractions from rat liver.

Significant differences are observed between the CD spectra of eu- and heterochromatin prepared by fractionating mechanically sheared rat liver chromatin on linear sucrose density gradients. Heterochromatin has a broad positive CD at 270--280 nm, a cross-over point at 256 nmn, and a negative shoulder at 248 nm. Euchromatin displays a shift in the positive peak to 267 nm and the cross-over point to 254 nm, as well as an intensification of the 267 nm peak. The negative shoulder at 248 nm is absent in euchromatin. These spectral differences between eu- and heterochromatin are present in both low and high ionic strength media. Mechanical shearing does not induce CD alteration and anomalous light scattering is absent in our system. The greater RNA content of euchromatin compared to heterochromatin cannot account for the spectral differences. These results suggest that the DNA conformation of euchromatin is distinct from that of heterochromatin and they may provide clues to the reasons for the greater transcription of euchromatin.

Animals↗
PubMed1976

Double-stranded DNA in methanol-ethanol-buffer solvent system.

DNA in a solvent system consisting of roughly equal volumes of methanol and ethanol and 5% buffer has a conservative circular dichroism (CD) spectrum of very low intensity above 220 nm and an increase of epsilon258 comparable to that of denatured DNA (about 40%). A direct comparison of this spectrum with the CD of single-stranded DNA reveals many differences, indicating DNA in this solvent system has a conformation different from that of denatured DNA. When the alcohols are removed, the B form conformation and normal epsilon258 are restored in native DNA, while single-stranded DNA remains denatured. A double-stranded structure of DNA in the methanol-ethanol-buffer solvent system is confirmed by the neutral cesium chloride density gradient centrifugation of DNA in which one chain is labeled with [14C]thymidine and the other [3H]5-bromodeoxyuridine. The doubly labeled DNA exposed to the alcohol solvent system has a centrifugal pattern identical with that of control DNA; the two radioactivities cosediment and form a superimposing band, distinctly different from that of single-stranded DNA; 3H-labeled (thymidine) chains sediment further than 14C-labeled chains (5-bromo-deoxyuridine). Denatured DNA exhibits varying CD spectra depending on solvents. It is suggested that single-stranded DNA in different solvent systems assumes different modes of base stacking.

Animals↗
PubMed1976

Origins of circular dichroism bands in Bowman-Birk soybean trypsin inhibitor.

The spectral properties of Bowman-Birk soybean trypsin inhibitor (BBI) were investigated by analyzing difference absorption spectra and difference CD spectra and by comparing them with those of tyrosyl model compounds. The O-acetylation of tyrosyl side chains showed that the ultraviolet CD bands of BBI above 225 nm originate from disulfide side chains and tyrosyl phenolic groups; phenylalanyl residues do not give rise to detectable CD in BBI in this wavelength region. The results of the tyrosyl ionization experiment were consistent with this interpretation. A broad negative CD band centered around 280 nm in BBI arises mainly from disulfide bonds (epsilonL - epsilonR = -0.83 M-1 cm-1 per disulfide). Each of 2 tyrosyl residues gives rise to negative CD in this region; together they contribute approximately 10% of the total CD intensity at 277 nm (epsilonL - epsilonR = -0.36 M-1 cm-1 per tyrosyl). Disulfide bonds in BBI also have a broad positive CD band centered around 240 nm (epsilonL- epsilonR = 0.9 M-1 per disulfide(. Tyrosyl side chains give rise to a sharp positive peak at 231 nm, overlapping with the positive disulfide CD. Dimerization of monomeric BBI did not alter the CD profile. One of two tyrosyl phenolic groups is relatively exposed and can be 0-acetylated by 100- to 1500-fold molar excess of N-acetylmidazole. The other is inaccessible to the reagent even in the presence of 8 M urea, but can be acetylated in the presence of 6 M guanidine hydrochloride. Fully acetylated BBI has the near-ultraviolet disulfide CD and the far-ultraviolet polypetide CD very similar to those of the native inhibitor, indicating the O-acetylation of two tryosyl side chains did not induce much conformational change in BBI. The near-ultraviolet CD of BBI was altered in the presence of 8 M urea of 6 M guanidine hydrochloride, with a greater change brought about by the latter. Dithiothreitol (20 mM) completely abolished the tyrosyl and disulfide CD in this region.

Binding Sites↗