The stepwise removal of histones from chicken erythrocyte nucleoprotein

1. A fractionation of chicken erythrocyte histones was achieved simultaneously with their extraction from saline-washed nuclei by stepwise titrations to progressively lower pH values. 2. Different acids and dilute buffer solutions of comparable pH behaved similarly in stepwise extractions of histones. 3. The histone preparations so obtained were characterized by their amino acid composition and behaviour on zone electrophoresis in starch gels. 4. The fractionation by titration was quite sharp at appropriate pH ranges, and the histone fraction that is apparently unique to avian erythrocytes was obtained without contamination by other histone fractions. 5. Histones prepared by stepwise titration were fractionated further by cation-exchange and exclusion chromatography. The chromatographic behaviour and amino acid composition of the components permitted comparison with histones prepared by other methods. 6. Histone fraction IIb was resolved into its subfractions IIb(1) and IIb(2) by exclusion chromatography on Bio-Gel P-60. 7. Histone fractions III and IV, previously reported to be absent from chicken erythrocyte nuclei, were found in extracts made at pH1.

Esters of serine and threonine in hydrolysates of histones and protamines, and attendant errors in amino acid analyses of proteins

1. Partial acid hydrolysates of histones from various origins and of protamine were analysed by a two-dimensional ionophoretic procedure to reveal strongly acidic ninhydrin-positive components. 2. Histone fractions prepared by extraction with sulphuric acid gave rise to spots identified as serine O-sulphate and threonine O-sulphate. These two compounds, which were not found in hydrolysates of corresponding fractions prepared by extraction with hydrochloric acid, were artifacts. 3. Hydrolysis of proteins in the presence of traces of sulphate can lead to the formation of the O-sulphates of serine and threonine. This can cause errors, which may sometimes be serious, in amino acid analyses of proteins. 4. O-Phosphoserine was obtained in small amounts from some histone fractions and from protamine, but was undetectable in other histone fractions, notably those of lower lysine content.

Interstitial Pregnancy after Homolateral Salpingectomy: (Report of a Case)

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