Clonal Decomposition and DNA Replication States Defined by Scaled Single-Cell Genome Sequencing

Accurate measurement of clonal genotypes, mutational processes, and replication states from individual tumor-cell genomes will facilitate improved understanding of tumor evolution. We have developed DLP+, a scalable single-cell whole-genome sequencing platform implemented using commodity instruments, image-based object recognition, and open source computational methods. Using DLP+, we have generated a resource of 51,926 single-cell genomes and matched cell images from diverse cell types including cell lines, xenografts, and diagnostic samples with limited material. From this resource we have defined variation in mitotic mis-segregation rates across tissue types and genotypes. Analysis of matched genomic and image measurements revealed correlations between cellular morphology and genome ploidy states. Aggregation of cells sharing copy number profiles allowed for calculation of single-nucleotide resolution clonal genotypes and inference of clonal phylogenies and avoided the limitations of bulk deconvolution. Finally, joint analysis over the above features defined clone-specific chromosomal aneuploidy in polyclonal populations.

clonealign: statistical integration of independent single-cell RNA and DNA sequencing data from human cancers

Measuring gene expression of tumor clones at single-cell resolution links functional consequences to somatic alterations. Without scalable methods to simultaneously assay DNA and RNA from the same single cell, parallel single-cell DNA and RNA measurements from independent cell populations must be mapped for genome-transcriptome association. We present clonealign, which assigns gene expression states to cancer clones using single-cell RNA and DNA sequencing independently sampled from a heterogeneous population. We apply clonealign to triple-negative breast cancer patient-derived xenografts and high-grade serous ovarian cancer cell lines and discover clone-specific dysregulated biological pathways not visible using either sequencing method alone.

Highly multiplexed single-cell quantitative PCR

We present a microfluidic device for rapid gene expression profiling in single cells using multiplexed quantitative polymerase chain reaction (qPCR). This device integrates all processing steps, including cell isolation and lysis, complementary DNA synthesis, pre-amplification, sample splitting, and measurement in twenty separate qPCR reactions. Each of these steps is performed in parallel on up to 200 single cells per run. Experiments performed on dilutions of purified RNA establish assay linearity over a dynamic range of at least 10⁴, a qPCR precision of 15%, and detection sensitivity down to a single cDNA molecule. We demonstrate the application of our device for rapid profiling of microRNA expression in single cells. Measurements performed on a panel of twenty miRNAs in two types of cells revealed clear cell-to-cell heterogeneity, with evidence of spontaneous differentiation manifested as distinct expression signatures. Highly multiplexed microfluidic RT-qPCR fills a gap in current capabilities for single-cell analysis, providing a rapid and cost-effective approach for profiling panels of marker genes, thereby complementing single-cell genomics methods that are best suited for global analysis and discovery. We expect this approach to enable new studies requiring fast, cost-effective, and precise measurements across hundreds of single cells.

Clonal analysis of individual human embryonic stem cell differentiation patterns in microfluidic cultures

Heterogeneity in the clonal outputs of individual human embryonic stem cells (hESCs) confounds analysis of their properties in studies of bulk populations and how to manipulate them for clinical applications. To circumvent this problem we developed a microfluidic device that supports the robust generation of colonies derived from single ESCs. This microfluidic system contains 160 individually addressable chambers equipped for perfusion culture of individual hESCs that could be shown to match the growth rates, marker expression and colony morphologies obtained in conventional cultures. Use of this microfluidic device to analyze the clonal growth kinetics of multiple individual hESCs induced to differentiation revealed variable shifts in the growth rate, area per cell and expression of OCT4 in the progeny of individual hESCs. Interestingly, low OCT4 expression, a slower growth rate and low nuclear to cytoplasmic ratios were found to be correlated responses. This study demonstrates how microfluidic systems can be used to enable large scale live-cell imaging of isolated hESCs exposed to changing culture conditions, to examine how different aspects of their variable responses are correlated.

Einwirkung von Natrium in flüssigem Ammoniak auf die Buntesalz-A-Kette von Schweineinsulin

In connection with synthetic work on insulin a study was made of the behaviour of natural A-chain-Buntesalt isolated from pig insulin after treatment with sodium in liquid ammonia. The A-chain was partially degradated and compounds with different amino acid compositions were built. It was possible to isolate the remaining intact A-chain as tetra-S-sulfonate by chromatography on DEAE-Sephadex with a yield of 55 per cent. This fraction gave, after recombination with isolated B-chain, the same yield of insulin as did A-chain undamaged by sodium.

Synthese einer teilgeschützten A-Kette des Schafinsulins

Die A-Kette des Schafinsulins wurde als teilgeschütztes Derivat Carbobenzoxy-glycyl-L-isoleucyl-L-valyl-L-glutamyl-L-glutaminyl-S-benzyl-L-cysteinyl-S-benzyl-L-cysteinyl-L-alanyl-glycyl - L- valyl - S - benzyl-L-cysteinyl-L-seryl-L-leucyl-L-tyrosyl-L-glutaminyl-L-leucyl-L-glutamyl-L-asparaginyl-L-tyrosyl-S-benzyl-L-cysteinyl-L-asparagin synthetisiert und in dieser Form durch Gelfiltration über Sephadex G 25 in wäßriger Lösung bei pH 8,5 — 8,7 gereinigt. Das synthetische Material entspricht dem natürlichen in biologischen und chemischen Testen.

Eine Synthese der Α-Kette des Schafinsulins unter ausschließlicher Verwendung säurelabiler Schutzgruppen

Die Α-Kette des Schafinsulins wurde als geschütztes Derivat Boc-Gly-Ile-Val-Glu (OBut) -Gln-Cys (Trt) - Cys (Trt) - Ala-Gly-Val-Cys (Trt) - Ser-Leu-Tyr (But) -Gln-Leu-Glu (OBut) - Asn-Tyr (But) - Cys (Trt) -Asn-OBzl ** aus fünf Fragmenten aufgebaut, durch Bromwasserstoff in Trifluoressigsäure von den Schutzgruppen befreit und zur Reinigung in das Tetra-S-sulfonat überführt. Nach Kombination mit B-Kette aus nativem Insulin lieferte das Präparat kristallines Insulin.

Zur Synthese von Dipeptiden des Arginin

N-Carbobenzoxypeptidäthyl- und -benzylester des ω-Nitro-L-arginins mit Glycin, DL-Alanin und DL-Serin wurden nach der Azid- und der Carbodiimidmethode dargestellt. Bei der Carbodiimidmethode entstanden als Nebenprodukte N- (Carbobenzoxyglycyl) -N,N′-dicyclohexylharnstoff, N- (Carbobenzoxy-DL-alanyl) -N,N′-dicyclohexylharnstoff und N- (Carbobenzoxy-DL-seryl) -N,N′-dicyclohexylharnstoff. Katalytische Hydrierung der Carbobenzoxy-Peptide und Carbobenzoxypeptidbenzylester führte zu den freien Peptiden.

Kleinwinkel-Röntgeninterferenzen bei nitrierter Seide

1. Naturseide wurde mit 0,15-und 1,5-n. Salpetersäure bei 100° und 40° C 2 bzw. 24 Stdn. lang nitriert. 2. Die eingebauten Tyrosinreste werden hierbei nitriert. Die Wanderungswege der Nitro-tyrosine auf dem Papyrogramm unter Verwendung von Isobutanol-Glykol-Essigsäure-Wasser als Lösungsmittel, bezogen auf Valin, betragen 0,74 für 3-Nitrotyrosin und 0,14 für 3.5-Dinitro-tyrcsin. 3. Beide Nitroseiden zeigen im Röntgenogramm auf dem Meridian außer dem bekannten Reflex bei 3,47 Ä drei weitere Reflexe (6,95, 10,36 und 20,9 Ä). Die Herkunft dieser Reflexe wird diskutiert. V r or kurzem wurde in dieser Zeitschrift über den

Eine neue Synthese der Α-Kette des Schafinsulins und deren Vereinigung mitnatürlicher B-Kette zu kristallinem, vollaktivem Insulin 1, 2

Die Α-Kette des Schafinsulins wurde in Form des Derivates BOC-Gly-Ile-Val-Glu (OBut)-Gln - Cys (BZL) - Cys (BZL) - Ala-Gly -Val-Cys (BZL) - Ser - Leu-Tyr-Gln-Leu-Glu (OBZL) - Asn - Tyr (BZL)-Cys (BZL) -Asn-OBZL 3 aus fünf Teilstücken, diese weitgehend unter Verwendung von tert.-Butyloxycarbonylaminosäure-Derivaten, aufgebaut. Die synthetische Α-Kette wurde nach Abspaltung der Schutzgruppen mit B-Kette aus Rinder-Insulin vereinigt und aus den Reaktionsprodukten das Insulin in reiner kristalliner Form isoliert.

Kombination synthetischer Insulinketten zu biologisch aktiven Präparaten

Äquimolare Mengen synthetischer Insulin-Α- und -B-Kette wurden in flüssigem Ammoniak durch Natrium gemeinsam von Schutzgruppen befreit und zu einem Präparat mit 0,2 — 1,0% Insulinaktivität oxydiert. Dessen biologische Wirksamkeit wurde durch Insulin-Antiserum vollständig gehemmt.

Kleinwinkel-Röntgeninterferenzen bei nitrierten Faserkeratinen

1. Menschen- und Roßhaar wurden mit 0.15—1,2-n. Salpetersäure bei 70—90- 24 Stdn. lang nitriert.

2. Die eingebauten Tyrosinreste werden zu 3-Nitro- und 3.5-Dinitrotyrosin nitriert. Ein Viertel der eingebauten Cystinbindungen und etwas mehr als die Hälfte der Säureamidgruppen werden umgesetzt. Wasserdampfaufnahme und Säurebindung der nitrierten Haare sind erheblich herabgesetzt.

3. Ein nitriertes Haarpräparat zeigt im Röntgenogramm auf dem Meridian Kleinwinkelreflexe bei 19,6; 24,4; 28,3; 39,3; 64.2 und 96,4 Å. Es wird angenommen, daß es sich um höhere Ordnungen einer Langperiode von 194 Å handelt, welche der etwas größeren Langperiode von 198—200 A des intakten α-Keratins entspricht. Ein nitriertes Roßhaar ergab im Röntgenogramm Meridian-Langperiodenreflexe, die einer Periode von 186 A entsprechen.

Synthese eines Nonapeptid-Derivates mit der N-terminalen Sequenz A 1-9 der Α-Kette des Schafinsulins

Als Derivat des N-terminalen Nonapeptids AI—9 der Α-Kette des Schafinsulins wurde Carbobenzoxy-glycyl-L-isoleucyl-L-valyl-L-glutamyl-γ-tert.-butylester-L-glutaminyl-S-benzyl-L-cysteinyl - S - benzyl-L-cysteinyl-L-alanyl-glycin durch Azidsynthese aus dem Carbobenzoxy-Tetrapeptid AI—4 und dem Seitenketten-geschützten Pentapeptid 45 — 9 dargestellt.

Synthese eines Pentapeptid-Derivates mit der C-terminalen Sequenz A 17-21 der Insulin-A-Kette

Das Derivat des C-terminalen Pentapeptids A 17 —21 der Insulin-Α-Kette Carbobenzoxy-L-glutamyl-γ-tert.-butylester-L-asparaginyl-L-tyrosyl-S-benzyl-L-cysteinyl-L-asparagin wurde durch gliedweisen Aufbau vom Carboxylende her über die p-Nitrophenyl-1 und N-Hydroxysuccinimidester2 oder durch Kondensation von Carbobenzoxy-L-glutamyl-γ-tert.-butyl-ester-L-asparaginyl-L-tyrosyl-azid mit S-Benzyl-L-cysteinyl-L-asparagin synthetisiert.

Contributions to the chemistry of human hair. 1. Analyses of cystine, cysteine and cystine oxides in untreated human hair

Synopsis Amino acid analysis, photometry and polarography were selected as analytical methods for the determination of thiol and disulphide groups in untreated human hair and the results are discussed. The pre-treatments necessary for the different analytical methods, e.g., hydrolysis, to some extent already induce chemical changes of the cysteine and cystine derivatives leading to method-dependent differences in the results. In many cases the partial oxidation products of cystine are supposed to be responsible for this effect. Electron Spectroscopy for Chemical Analysis (ESCA), as an analytical method for the determination of the cystine oxides, was found to be inapplicable due to insufficient resolution and sensitivity, whereas by the use of Fourier Transform Infrared (FTIR) Spectroscopy the sulphur-oxygen vibrations could be analysed and cystine monoxide and cystine dioxide were detected.

My journey from wool research to insulin

This paper is an autobiographical study of the author's early work on the chemical cross-linking of proteins as well as on oligomer and peptide synthesis from 1949 in Heidelberg until the synthesis of insulin in 1963 in Aachen.

Hair sulfur amino acid analysis

This overview emphasizes present aspects of sulfur-containing amino acids in hair. A selection of analytical procedures to determine cystine, cysteine, S-sulfocysteine, cystine oxide, cysteic acid, lanthionine and lysinoalanine are presented. The methods relate to intact hair or partial and total hydrolysates and comprise chromatography, titration, colorimetry, polarography and spectroscopy. For the analysis of cysteine, cystine and cystine oxides, polarography and spectroscopy are the methods of choice. Cysteic acid, lanthionine and lysinoalanine are analysed by means of ion-exchange chromatography (Spackman et al., 1958) after total hydrolysis.

Structure-function relationships of des-(B26-B30)-insulin

In order to study the role of the amino acid in position B25 and its environment in shortened insulins, a series of analogues was prepared with the following modifications: 1, Stepwise shortening of the B-chain including replacements of TyrB26 and ThrB27 by glycine; 2, substitutions at the carboxamide nitrogen of des-(B26-B30)-insulin-B25-amide by apolar, polar or charged residues of various chain lengths; 3, replacement of PheB25 by asparagine-amide, phenylalaninol or a series of alkyl and aralkyl residues. Trypsin-catalyzed semisyntheses were performed with Boc-protected or unprotected des-octapeptide-(B23-B30)-insulin and synthetic peptides. Relative receptor binding and in vitro bioactivity of [AsnB25]-des-(B26-B30)-insulin-B25-amide was 227 and 292% (on insulin), other activities ranged between 1 and ca. 200%. We make the following conclusions. An L-amino acid is essential in position B25. The B25-carbonyl and NH groups favour high binding and "superpotency", but are not indispensible for receptor contacts. For high affinity receptor interaction, the planarity at the C gamma-atom and the distance of B25-side-chain branching in position B25 are important, but an aromatic ring is not necessary.

Peptide analogues of the anaphylatoxin C3a; syntheses and properties

The chemical syntheses of C-terminally shortened analogues of C3a, which is the best investigated anaphylatoxin and derives from the third component of complement system, is reported. The peptide assembly was performed with the solid-phase technique using a polyamide support and an orthogonal protection strategy. The base-labile Fmoc group was chosen for N alpha protection in combination with acid-labile side-chain protection. Excellent acylation yields could be obtained using HBTU (O-benzotriazolyl-N,N,N',N'-tetramethyluronium hexafluorophosphate) as activating reagent. With this methodology we synthesized eighteen different peptides with the following modifications: Varying the peptide length by sequential addition of glycine or arginine residues, prolongating the N-terminus with the Fmoc- or Fmoc-aminohexanoyl residues and exchanging the glycine in position 74 for alanine or D-alanine. We obtained two C3a analogues, Fmoc-YRAAALALAR and Fmoc-Ahx-YRRGRAAALGLAR, which were shown to be substantially more active than native C3a in the guinea-pig-platelet assay.

Hormone binding site of the insulin receptor: analysis using photoaffinity-mediated avidin complexing

A trifunctional reagent was designed which allows derivatization of ligands, particularly peptides and proteins, for subsequent photoaffinity labelling of receptors and specific isolation of the covalent complex or its fragments. B29-(2-nitro-4-azidophenyl)-biocytinyl-insulin (NB-insulin) was synthesized, radioiodinated, and the B26-mono-iodo derivative isolated by HPLC. It was used to photoaffinity label human placental membranes and the purified insulin receptor. Extensive digestion of the covalent insulin-receptor complex with trypsin (EC 3.4.21.4) led to the generation of a fragment of Mr 14,000. Specific complexing with avidin, derivatized avidin or streptavidin could be demonstrated for the photoaffinity labelled alpha-subunit and the 14,000 core fragment. The latter was isolated (approx. 100 pmol from 3-4 placentae) by streptavidin affinity chromatography and HPLC. According to microsequencing based on the known primary structure of the insulin receptor, the N-terminus of the core peptide appears to be Leu20-His21-Glu22-Leu23. We thus conclude: a part of the insulin-binding region of the receptor is located close to the N-terminus of its alpha-subunit in a remarkably stable domain of the sequence 20--(approx.) 120.

Efficient synthesis of N alpha-acetylarginine methylamide

A simple preparation of Ac-Arg-(p-TosH or HCl)-NHMe is described. The NG-protonated Z-Arg was coupled with methylamine by the mixed anhydride method. Z-Arg-NHMe was purified as a NG-p-toluene sulfonate salt by crystallization from water. After removal of the Z group by catalytic hydrogenation and acetylation Ac-Arg(p-TosH)-NHMe was obtained. Ac-Arg(HCl)-NHMe was prepared by chromatography of the NG-TosH derivative on Dowex 44 (in Cl- form).

Shortened insulin with enhanced in vitro potency

After it has been shown that removal of residues B26-B30 leaves insulin with full biological activity, provided the new C-terminus is amidated (Fischer et al. (1985) Biol. Chem. Hoppe-Seyler 366, 521-525), it is demonstrated here that it does not even preclude enhancement of potency. 7 analogues of des-(B26-B30)-insulin-B25-amide were prepared by trypsin-mediated semisynthesis, the replacements being D-PheB24; HisB25, D-PheB25, TrpB25, TyrB25; D-PheB24,B25 and D-PheB24, TyrB25. Mere conversion of the configuration of B25-phenylalanine reduces in vitro potency to 0.5%. If B25-phenylalanine is, however, substituted by histidine or tyrosine activity is increased to 310 or 230, respectively. According to the features common to these two side chains, the favourable effect should be due to their ring structure with balanced aromatic and polar or H-bonding properties, respectively. The results indicate that in the complete insulin molecule the C-terminal pentapeptide modulates the subtle role that residues B24 and/or B25 play in receptor binding and activity; its presence may have a positive or negative effect. The drastic differences in activity between the shortened analogues are in no ways reflected in the CD spectra which are very similar, though clearly different from that of native insulin.

Structure-function relationships of shortened [LeuB25]insulins, semisynthetic analogues of a mutant human insulin

Replacement of B25-phenylalanine by leucine in the insulin sequence causes marked inactivation. The effect of this sequence variation was studied here in des-(B26-30)-insulin. [LeuB25]des-(B26-30)-insulin and its B25-amide were prepared by trypsin-mediated semisynthesis from N-terminally protected des-(B23-30)-insulin and synthetic tripeptides. The relative lipogenic potency in isolated rat adipocytes was 8.0% for the truncated analogue with a free B25-carboxyl function, and 18.1% for the amidated analogue. Binding to cultured human IM-9 lymphocytes was 4% and 9%, respectively. Thus, both shortened insulins are markedly more active than [LeuB25]insulin. The PheB25----LeuB25 substitution in both the shortened and the full sequence has a moderate effect on the CD spectrum, indicating that the gross main chain conformation is largely retained in both molecules. Independent of the substitution an absolute increase of the circular dichroism is observed upon amidation of the B25-carboxyl group.

The synthesis and some biological properties of N-(6-purinyl)peptides

The chemical synthesis and biological properties of N-(6-purinyl)peptides are described. N-(6-Purinyl)amino-acid derivatives were synthesized and condensed with amino acid esters and peptide esters using the dicyclohexylcarbodiimide/N-hydroxysuccinimide method. The products were isolated via gel filtration on Sephadex G-10 in 0.05M NH4HCO3 followed by either ion exchange chromatography on SP-Sephadex or by preparative HPLC. The methyl esters were saponified and the tert-butyl ester group was removed by treatment with trifluoroacetic acid without damaging the purinyl residue. N-(6-Purinyl)peptides were characterised by chromatographic and spectroscopic methods. Acid hydrolysis of N-(6-purinyl)-L-amino acids caused the racemization of the neighbouring L-amino acid. Model studies were performed with N-(6-purinyl)-L-alanine, N-(6-purinyl)-D-alanine, N-(6-purinyl)-L-alanyl-L-leucine and N-(6-purinyl)-D-alanyl-L-leucine. After acid hydrolysis the N-(6-purinyl)amino acids were totally racemized and the N-(6-purinyl)dipeptides formed 14% of the enantiomer of alanine. The N-(6-purinyl)-omega-amino acids and the N-(6-purinyl)peptides were screened in a limited number of tests as immunomodulators (antibody-secretion, phagocytosis, cytostatic activity of macrophages) and as cytotoxic agents.

A shortened insulin with full in vitro potency

Des[(B26-30)-pentapeptide]insulin-B25-amide was prepared from protected des-[(B23-30)-octapeptide]insulin (pig) and H-Gly-Phe-Phe-NH2 by trypsin-mediated semisynthesis in a yield of 9% (based on insulin). The analogue was characterized with respect to chemistry, biological function and CD spectroscopy. While des[(B26-30)-pentapeptide]insulin with free carboxylate group exhibited a typical insulin activity of only 25% in vitro, des[(B26-30)-pentapeptide]insulinamide was fully active. Therefore des[(B26-30)-pentapeptide]insulin meets all structural and dynamic requirements for recognition and binding of the receptor as well as exertion of the biological effect, provided that the negative charge in the hydrophobic environment of PheB25 is neutralized.

Immunostimulating hexapeptide from human casein: amino acid sequence, synthesis and biological properties

A hexapeptide obtained from human casein by enzymatic digestion has been purified, sequenced and synthesized; its structure is: Val-Glu-Pro-Ile-Pro-Tyr. In vitro this hexapeptide stimulates the phagocytosis of opsonized sheep red blood cells by murine peritoneal macrophages. Administered intravenously to adult mice, it enhances the resistance to infection with Klebsiella pneumoniae.

[B17-D-leucine]insulin and [B17-norleucine]insulin: synthesis and biological properties

The chemical synthesis of two porcine insulin analogues is described. Leucine in position B17 of the native molecule was substituted by its D-enantiomer and by L-norleucine, respectively. Both B-chain derivatives were synthesized by fragment condensation and purified as di-S-sulphonates by gel filtration followed by ion exchange chromatography on SP-Sephadex at pH3. Combination with native sulphhydryl A-chain yielded [DLeuB17]insulin and [NleB17]insulin. Both insulin analogues were isolated by gel filtration followed by ion exchange chromatography on CM-cellulose at pH 4.0. Biological activities of the analogues were determined relative to native pork insulin: 1) glucose oxidation in rat epididymal adipocytes was 6% for [DLeuB17]insulin and 16% for [NleB17]insulin, 2) receptor-binding affinity tested with cultured human fibroblasts and with rat adipocytes was 3% for [DLeuB17]insulin and 26% for [NleB17]insulin, and 3) thymidine incorporation into DNA of human fibroblasts was 35% for [DLeuB17]insulin and 100% for [NleB17]insulin.

The synthesis of [A 19-3-iodotyrosine] and [A 19-3,5-diiodotyrosine]insulin (porcine)

The chemical synthesis of [Tyr(I)A19] and [Tyr(I2)A19]insulin (porcine), using the amino-acid derivatives 3-iodotyrosine and 3,5-diiodotyrosine is described. The synthesis of the iodinated A-chains were performed by segment condensation in solution using acid labile protecting groups. The hydroxyl groups of Tyr(I) and Tyr(I2) were unprotected. For the temporary protection of the alpha-amino groups of the A-chain segments containing iodinated tyrosines, the 1-(4-biphenylyl)-1-methylethoxycarbonyl group was selected. After deprotection and sulphitolysis the iodinated A-chain tetra-S-sulphonates were purified by ion exchange chromatography on DEAE cellulose at pH 5.6. Reduction to the sulphhydryl form and the combination with native porcine B-chain yielded [Tyr(I)A19] and [Tyr(I2)A19]insulin (porcine), respectively. Purification of the first product was achieved by gel filtration and of the later by ion exchange chromatography on CM-cellulose at pH 4.5 and gel filtration. The monoiodinated insulin had a biological activity of 24 +/- 2% and the diiodinated analogue 2.6 +/- 0.2% as determined in an in vitro lipogenesis assay with epididymal adipocytes.

[Increased yields of insulin by recycling of non-combined insulin chains]

The yield of insulin by the combination of reduced A and B chains is increased from 15% to 33-34% if the non-insulin-containing fractions of the gel filtration are isolated and used for further combinations (recycling). Crude insulin recovered by gel filtration can be highly purified by preparative high-performance liquid chromatography. Lower yields of insulin were obtained on recombination of chains which had been recycled five times or more. Sulfur analyses show a loss of cystine sulfur. The occurrance of lanthionine and lysinoalanine indicates an alkaline destruction of cystine/cysteine during the repeated combination steps.

[B22-D-arginine]insulin: synthesis and biological properties

An analogue of porcine insulin which differs from the native molecule in that the amino-acid residue B22-L-arginine is replaced by its D-enantiomer has been synthesized. The [D ArgB22]B-chain was synthesized by the segment condensation method and purified as the di-S-sulfonate by ion exchange chromatoggraphy on SP-Sephadex at pH 3.5. Combination with native porcine sulfhydryl A-chain gave [DArgB22]insulin which was purified by ion exchange chromatography on SP-Sephadex at pH 4.5 with a linear NaCl gradient. The biological activity of this analogue as measured by glucose oxidation in rat epididymal adipocytes was 2%. Thymidine incorporation into DNA of human fibroblast was 16%. The immunoreactivity using antipork insulin antibody in a double antibody immunoassay was 4%. The receptor-binding affinity as measured by radioreceptor assays was 2% with cultured human fibroblasts and 1% with rat adipocytes. These results suggest that the L-configuration at B22-arginine is essential for retaining the biological, immunological and receptor-binding properties of the hormone.

[Synthesis of two median segments of human parathyrin (author's transl)]

Human parathyrin-(32-43)-dodecapeptide (H-His-Asn-Phe-Val-Ala-Leu-Gly-Ala-Pro-Leu-Ala-Pro-OH) and tyrosyl-[human parathyrin-(43-55)-tridecapeptide] (H-Tyr-Pro-Arg-Asp-Ala-Gly-Ser-Gln-Arg-Pro-Arg-Lys-Lys-Glu-OH) were prepared, using the strategy of segment condensation in combination with acid-labile protecting groups. The peptides will be utilized for radioimmunoassay and receptor-binding studies.

Characterization of two anti-human parathyrin antisera

Two anti-human parathyrin antisera were raised in sheep. These were characterized by radioimmunoassay using two commercially available bovine parathyrin preparations and one synthetic human parathyrin fragment (sequence 42-55 (42-Tyr)) for radioiodination. In addition, four synthetic human parathyrin fragments (sequences 1-34, 32-43, 434-68, 53-84), one bovine parathyrin peptide (sequence 28-48) and a human parathyrin standard from a tissue culture containing the intact hormone were utilized in a competitive inhibition assay against the two radiolabelled bovine parathyrin preparations. On column chromatography, both tracers revealed a difference in molecular weight, which is believed to be related to the extraction technique. The sequence fragment 44-68 of human parathyrin had the highest affinity for the two antisera when using the smaller molecular weight tracer and there were no qualitative changes observed in the presence of plasma. Using the higher molecular weight tracer, the addition of plasma to one of the antisera resulted in a higher affinity for the sequence fragment 1-34 of human parathyrin compared to that of intact parathyrin. Antiserum from a second sheep remained specific only for the mid-region (sequence 44-68) of the parathyrin molecule independent of the tracer used. Due to the antiserum's constant characteristic, it revealed a high reliability for the discrimination between plasma parathyrin levels in normal probands and in patients with hyperparathyroidism. Our data demonstrate that the specificity of the radioimmunoassay for human parathyrin is not exclusively dependent on the antibody source, but also on the tracer preparation and the protein content of the incubation medium.

Characterisation of the binding sites of anti-parathyroid hormone antisera using synthetic parathyroid hormone peptides

Four antisera raised against partly purified PTH preparations all showed a wide range of specificities when reacting with radioiodinated PTH peptides representing several different portions of the intact hormone sequence. In contrast, antisera raised against individual peptides were only able to cross-react with other peptides that contained all or part of their amino acid sequence in common. Cross-reacting peptides were seen to contain one or more amino acid residues having high interspecies variability in common. We have explained the antigenicity and cross-reactivity of the peptides on the basis of these common highly variable amino acid sequences. We have concluded that the selection of hormonal material in radioimmunoassays for PTH should be made on the basis of the highly variable amino acid residue content. This will allow a narrowing of the assay specificities and permit detection of a desired region of the PTH hormone.

[An improved method for the combination of modified insulin chains (author's transl)]

A procedure is described in which the yields of the combination of insulin A and B chains, especially of modified chains, are increased. The chains are reduced simultaneously in 8M urea buffer at pH 8.6 with 2-mercaptoethanol. The thiol chains are not isolated but transferred to the oxidation buffer at pH 10.6 by means of gel chromatography on Sephadex G-25. During the chromatography about 50% of the tetrathiol A chain is oxidized specifically to a dithiol A chain disulphide, in which presumably the 6,11-disulphide ring is closen. Generally we observed that the combination yields of modified A or B chains are lower than the yields of combinations of unmodified A or B chains. It seems that there is a correlation between the biological activity of the analogue and the yield obtained by the recombination of the chains.