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PubMed1997

The influence of 5-azacytidine on the condensation of the short arm of rye chromosome 1R in Triticum aestivum L. root tip meristematic nuclei.

This paper describes the effects of 5-azacytidine on the condensation state of rye (Secale cereale L.) chromatin introduced into the wheat genome (Triticum aestivum L. cv. Beaver). The wheat cultivar Beaver carries a translocation between the short arm of rye chromosome 1R (1RS) and the long arm of wheat chromosome 1B (1BL/1RS). 1RS can be detected using genomic in situ hybridisation and carries a ribosomal DNA (rDNA) locus that can be simultaneously detected using multiple labelling strategies. The rDNA locus divides 1RS into a distal region that is gene rich and a proximal region that is gene poor and highly methylated. 1RS also carries a large block of subtelomeric heterochromatin. The drug, which acts to inhibit DNA methylation in plants, has three pronounced effects on interphase nuclei. (1) It induces aberrant condensation of the rye subtelomeric heterochromatin and in many cases induces sister chromatid separation in the subtelomeric heterochromatin of G2 nuclei. (2) Nuclei trisomic for 1RS are observed at low frequency in treated material and are probably a consequence of aberrant sister chromatid separation or condensation. (3) The drug alters normal condensation of 1RS euchromatin. However, contrary to expectation the effect is not simply to induce decondensation. The proximal region of the arm actually condenses at low levels of drug administration while the distal region remains unaltered or increases its decondensation state. Increasing the concentration of 5-azacytidine induces a biphasic response and at the highest concentration used all regions of the arm show signs of decondensation. Thus the influence of the drug on chromatin condensation depends on the genomic structure.

Azacitidine↗

PubMed2000

Non-apoptotic chromosome condensation induced by stress: delineation of interchromosomal spaces.

Chromosomes are known to occupy distinct territories, suggesting the existence of definite borders. Visualization of these borders requires chromatin condensation like that seen in prophase cells. We developed a novel method to induce chromosome condensation in all cells regardless of cell cycle stage using a complex set of stresses. The cells were not apoptotic, as indicated by the absence of DNA damage, maintenance of the intact lamina and scaffold attachment factor A, and by the continuation of metabolic processes as well as proliferative capacity. That the appearance of chromosome condensation did not represent a premature mitotic event was shown by the absence of fibrillarin and Ki67 envelopment of chromosomes, continued protein synthesis and the reversibility of chromosome condensation. That chromosome condensation was achieved was demonstrated by the removal of chromatin from the nuclear envelope and chromosome painting. Specific genetic sites known to be at the surface of chromosomes retained their positions as shown by in situ hybridization. Stress-induced chromosome condensation was used to prove that specific nuclear domains such as ND10 are interchromosomally located and that green fluorescent protein-tagged ND10-associated proteins are useful markers for chromosomal boundaries after adenovirus 5 track formation in vivo. From these observations we conclude that chromosomal territories appear to have boundaries that exclude developing macromolecular aggregates.

Apoptosis↗

PubMed1987

Analysis of the condensation step in elongation of very-long-chain saturated and tetraenoic fatty acyl-CoAs in swine cerebral microsomes.

The condensation products in the elongation of exogenous arachidoyl-CoA (20:0-CoA) and endogenous fatty acids in adult swine cerebral microsomes were isolated and purified by using HPLC and a radioanalyzer. A saponification product of the condensation reaction of 20:0-CoA with malonyl-CoA was identified by gas chromatography-mass spectrometry as 2-heneicosanone (21:0-2-one). The endogenous substrates (16:0-CoA and 20:4-CoA) were likewise identified as 2-heptadecanone (17:0-2-one) and 2-heneicosatetraenone (21:4-2-one). Quantitative analysis of condensation activity was performed using electron-impact mass fragmentography. A characteristic fragment ion (m/z 59) of 21:0-2-one was used to estimate the condensation activity for 20:0-CoA, and fragment ions at m/z 58 and 80 were monitored for the endogenous substrates (16:0-CoA and 20:4-CoA, respectively). The molecular ion for each product was detected using chemical ionization. A comparative study of the condensation of 20:0-CoA and endogenous substrates was carried out for microsomes obtained from white matter, gray matter, and isolated neuronal cells; the activity for 20:0-CoA was significantly lower in gray matter and neuronal cells than in white matter, whereas the activity for endogenous substrates was almost the same for microsomes obtained from gray and white matter. This result suggests that the condensation enzyme for 20:0-CoA may be different from that for endogenous 16:0-CoA or 20:4-CoA in swine cerebral microsomes.

Acyl Coenzyme A↗

PubMed1987

Comparison between condensation and overall chain elongation of arachidoyl-CoA and arachidonoyl-CoA in swine cerebral microsomes.

The condensation and overall elongation products of exogenous arachidoyl-CoA (20:0-CoA) and endogenous fatty acids in swine cerebral microsomes were detected by radio gas chromatography. In addition, the condensation products with malonyl-CoA as substrate were analyzed by radio high-performance liquid chromatography. Three main condensation products were detected; the overall elongation products of exogenous 20:0-CoA were 22:0 and 24:0, and those of endogenous substrates were 18:0, 22:4, and 24:4. The yield was estimated for the conversion of 3-ketoacyl-CoAs to the corresponding saponification products (methyl ketones or R-2-one; e.g., 2-heptadecanone = 17:0-2-one); these products were identified in the preceding paper (S. Yoshida and M. Takeshita (1987) Arch. Biochem. Biophys. 254, 170-179). The extraction of R-2-one by hexane depended on the acyl chain length. The yield of 2-heneicosanone (21:0-2-one) detected by radio gas chromatography was 80% whereas the yields of 17:0-2-one and 2-heneicosatetraenone (21:4-2-one) from the corresponding 3-ketoacyl-CoAs were 56 and 48%, respectively. A quantitative comparison was performed for the condensation and overall elongation activity; it was noticed that the condensation activity for the system which simultaneously produced two elongation products was nearly the same as that of the corresponding overall elongation activity. This result suggests that the condensation step may be at least one of the rate-limiting steps in the overall elongation of very-long-chain fatty acyl-CoA.

Acyl Coenzyme A↗

PubMed1992

Condensation activity for polyunsaturated fatty acids with malonyl-CoA in rat brain microsomes. Characteristics and developmental change.

Condensation activities for gamma-linolenic acid (18:3(n-6)), octadecatetraenoic acid (18:4(n-3)) and eicosapentaenoic acid (20:5(n-3)) with malonyl-CoA were measured and compared with the condensation activities for 16:0-CoA, 18:1-CoA, 18:2(n-6)-CoA and 18:3(n-3)-CoA in rat brain microsomes of various ages. The age-dependence of condensation activities for 18:3(n-6), 18:4(n-3) and 20:5(n-3) showed a maximum at 1- to 2-month-old and were still higher at 3-month-old 2- to 3-fold than the activities in microsomes of pups. Conversely, the age-dependence of condensation activity for 16:0-CoA showed a peak around 1 month-old, but decreased at 3-month-old to the level of the activities in pups. The condensation activity for 20:5(n-3) was inhibited by 18:3(n-6) or 18:4(n-3) and the inhibition was not competitive. The condensation of 18:3(n-6) was also inhibited by 18:4(n-3) in the same manner. A physiological implication of the inhibition system at the substrate level was discussed.

Animals↗

PubMed1977

Relation between chemical constituents of tobacco and mutagenic activity of cigarette smoke condensate.

Mutagenic activities of cigarette smoke condensate were assayed in the presence of S-9 Mix using Salmonella typhimurium TA 98. The results were examined in relation to chemical data of tobacco leaves. Among the nitrogenous constituents examined, the contents of total nitrogen and protein nitrogen and the soluble nitrogenous fraction were positively and significantly related to an increase in mutagenic activity of the smoke condensate, whereas nicotine and nitrate were not important in contributing to mutagenic potency of such condensates. The age of tobacco leaves influenced the mutagenic potency of the condensate, which was lowest in leaves from the lower stalk position and increased with ascending leaf position on the stalk. Smoke condensate from tobacco with higher sugar content resulted in lower mutagenic activity. The present results, together with the previous study on the mutagenicity of the amino acid pyrolyzates, suggest that potent mutagens in cigarette smoke condensate are nitrogen-containing compounds, which may be formed from proteins and amino acids during the burning of a cigarette.

Amino Acids↗

PubMed1989

Micrococcal nuclease digestion study of spermidine-condensed DNA.

Spermidine-condensed lambda DNA tertiary structures have been studied by micrococcal nuclease digestion. Broad but discrete DNA bands were observed in gel electrophoresis experiments of digests at sizes of: 1003 +/- 115 bp, 1972 +/- 190 bp and 3100 +/- 350 bp. These bands comprise an arithmetic series, similar to, but larger than, arithmetic DNA band series sizes we have observed previously in calf thymus and phi x-174 DNA condensates. The 1003bp monomer lambda DNA band size corresponds to wrapping B DNA once circumferentially about the toroidal-shaped tertiary structures, the predominant condensed structures present in these preparations, and is consistent with the measured electron microscopic dimensions for hydrated lambda DNA toruses previously presented. DNA fragment length stability was determined by release from the digested condensates. Fragments of 80-85bp and sizes below are thermodynamically unstable in the lambda DNA condensates. This fragment size agrees well with a recent determination of the cooperativity size in DNA condensates.

Animals↗

PubMed1988

Prostacyclin and thromboxane formation following chronic exposure to cigarette smoke condensate administered via osmotic pumps in rats. A method for chronic administration of particulates of whole smoke.

Chronic cigarette smoke exposure in vivo causes decreased conversion of [14C]arachidonic acid (AA) to prostacyclin (PGI2) by isolated aortic tissue and increased conversion to thromboxane (TXA2) by isolated platelets from rats. Alterations in the PGL2/TXA2 balance may be part of the mechanism by which smoking increases the risk of cardiovascular disease. In order to ascertain whether the particulate phase of whole smoke alone could cause these changes, rats were administered smoke condensate in propylene glycol for 56 days via two Alzet (2ML4) osmotic pumps. Pumps containing vehicle, low dose (150 micrograms/hr) or high dose (300 micrograms/hr) condensate were implanted s.c. dorsal to the thoracic vertebrae in male Sprague-Dawley rats. Three-quarters of the condensate-treated rats developed fibrin cysts encapsulating the pumps. Cysts were not seen in vehicle-treated rats. Residual pump contents were weighed and analyzed by GLC to ensure condensate delivery. No significant difference in weight gain patterns between sham-operated and treatment groups were observed. Vehicle had no effect on aortic PGI2 or platelet TXA2 formation compared to sham. Low-dose condensate was without effect on PGI2/TXA2 formation. In high-dose condensate-treated rats, PGI2 and TXA2 formation were 84% and 136%, respectively, of the vehicle control (n.s.). Pump encapsulation may be a limiting factor in the administration of complex particulate suspensions.

Animals↗

PubMed1980

Mutagenicity of smoke condensates from joss sticks.

Smoke condensates obtained from 8 Japanese brands of joss sticks were assayed for mutagenicity on Salmonella typhimurium TA100 and TA98 with and without metabolic activation by S9 mix. An average of 22 mg of smoke condensate was obtained per joss stick weighing about 0.3 g. Smoke condensates obtained from all the joss sticks tested showed definite mutagenicity with a linear dose response on both tester strains of bacteria with metabolic activation. Without S9 mix, the smoke condensates from some of the joss sticks also showed positive mutagenicity on TA100 at 0.15 or 0.3 mg/plate. The revertant numbers over the background counts induced by 1-mg samples of the smoke condensates from joss sticks with S9 mix were 140--310 with TA100 and 90--200 with TA98. These values were one-fifth to half that of cigarette smoke condensate with TA100 and one-fourteenth to one-fifth that with TA98. However, it was calculated that, when joss sticks are burnt continuously in a closed space under the usual conditions, the mutagenicity of their smoke per unit volume of air is similar to that of the smoke produced by the smoking of two cigarettes per hour. Extracts of unburnt joss sticks with methanol, chloroform or dimethylsulfoxide had no mutagenicity, showing that the burning process produces the mutagenic substance(s).

Genetic Techniques↗

PubMed1989

The liquid condensed diffusional transition of dipalmitoylphosphoglycerocholine in monolayers.

The fine details of the phase transition of dipalmitoylphosphoglycerocholine (DPPC) monolayers at air/NaCl solution interfaces were investigated at 21 +/- 1 degrees C by using the fluorescence after photobleaching technique employing 12-(9-anthroyloxy)stearic acid as fluorescent probe. The mode of compression of the monolayer (i.e., continuous compression or successive additions of the lipid at fixed area) together with the ionic strength of the subphase (0.1 or 1.0 M NaCl) were particularly studied. The photobleaching results show that the lateral diffusion coefficient of the probe molecules decreases drastically within the liquid-condensed phase, i.e., from the end of the liquid-expanded-liquid-condensed phase transition to the beginning of the solid-condensed phase. The molecular areas at which the phase transition occurs under the various experimental conditions, together with a parallel analysis of the hydration states and related molecular areas of the DPPC molecules in multilayers, strongly suggest that the steric hindrance associated with the hydration water of the polar head of DPPC molecules in the monolayer is responsible for the drastic decrease in diffusion coefficient in the liquid-condensed phase. Furthermore, the fluorescence characteristics of the probe molecules also show that, together with the aforementioned reorganization of the polar head, a structural reorganization of the aliphatic chains of the lipid molecules also takes place in the liquid-condensed phase. The liquid-condensed phase therefore appears as a transition region from liquid to solid phases in which the lipid molecules present a significant decrease in their lateral diffusion related to a structural reorganization of both their polar and aliphatic components.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1983

On the contribution of polycyclic aromatic hydrocarbons to the carcinogenic impact of automobile exhaust condensate evaluated by local application onto mouse skin.

The objective of this investigation was to identify the substances chiefly responsible for the carcinogenicity of automobile exhaust condensate using topical application onto the skin of mice. This was performed by comparing the carcinogenic effect of various fractions with that of an unseparated sample of automobile exhaust condensate, tested in 3 different doses. The probit and Weibull analysis of the result shows: (a) The condensate, emitted from a gasoline-driven automobile provokes local tumors after long-term application to the dorsal skin of mice. The tumor incidence demonstrates a clear cut dose-response relationship. (b) The fraction of polycyclic aromatic hydrocarbons (PAH) containing more than 3 rings accounts for about 84-91% of the total carcinogenicity of automobile exhaust condensate. This fraction represents only about 3.5% by wt of the condensate. (c) The content of benzo[a]pyrene (BaP) (0.414 mg/g) accounts for 6-7.6% of the total carcinogenicity of automobile exhaust condensate, 15 selected PAHs for about 41%. (d) Regarding the minor effect of the PAH-free fraction (about 83% by wt), no hints for a cocarcinogenic activity were observed.

Animals↗

PubMed2005

Surface complexation of condensed phosphate to aluminum hydroxide: an ATR-FTIR spectroscopic investigation.

Two model compounds, sodium pyrophosphate (pyro-P) and sodium tripolyphosphate (tripoly-P), were employed to elucidate the binding mechanisms of condensed phosphate on aluminum hydroxide by utilizing attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Peak assignments for the condensed phosphates in the solution phase and those adsorbed on the surface of aluminum hydroxide were made. Electron delocalization and polarization were employed to explain the peak shifts and the complexation of condensed phosphate with aluminum hydroxide. The tripoly-P and pyro-P were adsorbed on aluminum hydroxide by forming inner-sphere complexes. The adsorbed condensed phosphates were deprotonated in the pH range from 4 to 10. Monodentate, bidentate, and binuclear complexes were formed when pyro-P was adsorbed on aluminum hydroxide, while monodentate and binuclear complexes were formed when tripoly-P was adsorbed. Based on the FTIR data, we proposed that when either bidentate or binuclear complexes were formed, the two oxygen atoms participating in the complexation with aluminum hydroxide could not be originated from the same terminal phosphate moiety. The AlO bond formed in the complexation of pyro-P or tripoly-P with aluminum hydroxide (AlPO(-3)) was not as strong as the HO bond in terminal HPO(-3). The bridging PO(-2) of tripoly-P did not coordinate with aluminum hydroxide. The real-time ATR-FTIR study on condensed phosphate adsorption revealed that a long contact time between condensed phosphates and aluminum hydroxide particles can result in a transformation of an initially formed species into a thermodynamically more stable phase.

Adsorption↗

PubMed2005

Condensation of the central nervous system in embryonic Drosophila is inhibited by blocking hemocyte migration or neural activity.

Condensation is a process whereby a tissue undergoes a coordinated decrease in size and increase in cellular density during development. Although it occurs in many developmental contexts, the mechanisms underlying this process are largely unknown. Here, we investigate condensation in the embryonic Drosophila ventral nerve cord (VNC). Two major events coincide with condensation during embryogenesis: the deposition of extracellular matrix by hemocytes, and the onset of central nervous system activity. We find that preventing hemocyte migration by removing the function of the Drosophila VEGF receptor homologue, Pvr, or by disrupting Rac1 function in these cells, inhibits condensation. In the absence of hemocytes migrating adjacent to the developing VNC, the extracellular matrix components Collagen IV, Viking and Peroxidasin are not deposited around this tissue. Blocking neural activity by targeted expression of tetanus toxin light chain or an inwardly rectifying potassium channel also inhibits condensation. We find that disrupting Rac1 function in either glia or neurons, including those located in the nerve cord, causes a similar phenotype. Our data suggest that condensation of the VNC during Drosophila embryogenesis depends on both hemocyte-deposited extracellular matrix and neural activity, and allow us to propose a mechanism whereby these processes work together to shape the developing central nervous system.

Animals↗

PubMed2001

Simple simulations of DNA condensation.

Molecular dynamics simulations of a simple, bead-spring model of semiflexible polyelectrolytes such as DNA are performed. All charges are explicitly treated. Starting from extended, noncondensed conformations, condensed structures form in the simulations with tetravalent or trivalent counterions. No condensates form or are stable for divalent counterions. The mechanism by which condensates form is described. Briefly, condensation occurs because electrostatic interactions dominate entropy, and the favored coulombic structure is a charge-ordered state. Condensation is a generic phenomenon and occurs for a variety of polyelectrolyte parameters. Toroids and rods are the condensate structures. Toroids form preferentially when the molecular stiffness is sufficiently strong.

Biophysical Phenomena↗

PubMed1984

An analysis of the contribution of the preparatory technique to the appearance of condensed and orthodox conformations of liver mitochondria.

The structure and volume of isolated mitochondria embedded for electron microscopy during different respiratory states were analyzed in thin sections. Three different embedding methods were compared; osmium tetroxide fixation/acetone dehydration, glutaraldehyde fixation/acetone dehydration, and glutaraldehyde fixation-osmium tetroxide postfixation/acetone dehydration. Analysis of fresh mitochondria, isolated in a sucrose medium, revealed the presence of a homogeneous population with respect to structure when any of the three methods were applied. After fixation with osmium alone, or in combination with glutaraldehyde, nearly 100% of the mitochondria were in a "condensed" conformation. Mitochondria fixed with glutaraldehyde alone resulted in a population of mitochondria that had large spaces separating the two membranes of the cristae which corresponds to the condensed conformation as observed after osmium fixation. Transfer of the mitochondria to the incubation medium led to the appearance of two classes of mitochondria with respect to size. One class had a volume close to that observed when suspended in sucrose, and another class was present that was 30-45% larger. In osmium fixed or in double-fixed preparations, these small and large classes corresponded to "condensed" and "orthodox" forms of mitochondria respectively. When glutaraldehyde was used alone as the fixative, the two size classes were also present. However, the mitochondria were homogeneous with respect to structure. In these mitochondria, the width of the space that separated the cristae membranes had become reduced when compared to mitochondria suspended in sucrose. The two size classes were also present in samples of mitochondria prepared during both states 3 and 4. State 4 conditions did not lead to any significant increase of the number of condensed mitochondria. In state 3 preparations, 65-70% of the population were condensed. The condensed and orthodox forms could be related to normal and swollen forms of mitochondria. Conditions that led to a swelling also led to an increase in the number of orthodox mitochondria in osmium-fixed material. The different appearance of the mitochondria is explained by the different conditions for fixation of the mitochondria that exist when nonswollen and swollen mitochondria are fixed. This difference is particularly crucial in the case of osmium tetroxide due to the unique way this fixative, among generally used fixatives, denatures proteins.

Acetone↗

PubMed2003

MALDI-TOF mass spectrometry and PSD fragmentation as means for the analysis of condensed tannins in plant leaves and needles.

MALDI-TOF mass spectrometry and 13C NMR spectroscopy were applied to unveil typical characteristics of condensed tannins of leaves and needles from willow (Salix alba), spruce (Picea abies) and beech (Fagus sylvatica) of three tree species that are ubiquitous in German forests and landscapes. For further evaluation, lime (Tilia cordata) was included. The 13C NMR spectroscopy confirmed the purity of the condensed tannin fractions and the efficiency of the procedure used for their extraction. While signals representative for procyanidin units are observable in all liquid-state 13C NMR spectra, resonance lines of prodelphinidin were only detected in those obtained from the condensed tannins of spruce needles and beech leaves. Typical signals in the chemical shift region between 70 and 90 ppm demonstrated the presence of stereoisomers (catechin/epicatechin; gallocatechin/ epigallocatechin). The MALDI-TOF mass spectra of the condensed tannins show signals of polymers of up to undecamers. Supporting the observations from the NMR spectroscopy, the mass spectra of the willow and lime leaf condensed tannins were identified as polymers with mainly procyanidin units, while the polymers of the spruce needle and beech leaves exhibit varying procyanidin/prodelphinidin ratios. Post source decay (PSD) fragmentation lead to a sequential loss of monomers and allowed a detailed characterization and sequencing of individual chains. In the case of the condensed tannins of lime this technique clearly excludes a pelargonidin terminal unit followed by a prodelphinidin unit, which would result in the same molecular masses as a polymer solely built up of procyanidin units.

Biflavonoids↗

PubMed1998

Involvement of cumulus cells stimulated by FSH in chromatin condensation and the activation of maturation-promoting factor in bovine oocytes.

The effects of FSH-stimulated cumulus cells on the regulatory mechanisms of chromatin condensation and maturation-promoting factor (MPF) activation around the time of germinal vesicle breakdown (GVBD) in bovine oocytes were examined. Chromatin condensation occurred in oocytes arrested at the germinal vesicle (GV) stage by protein synthesis inhibitor, cycloheximide, but this condensation was blocked by FSH-stimulated cumulus cells. However, treatment with cyclic AMP (cAMP)-dependent protein kinase inhibitor, H-8, dramatically increased the proportion of oocytes possessing GVs with condensed bivalents. Under the condition of inhibited protein synthesis, the phosphorylation form of p34cdc2 kinase was not changed due to chromatin condensation, although the activity of histone H1 kinase was significantly increased compared with that of oocytes possessing GVs with filamentous bivalents. The cycloheximide-dependent GVBD block was overcome by okadaic acid (OA) in 48 and 13% of the oocytes in the absence and presence of FSH, respectively. An initial 6-h culture period critical for protein synthesis was necessary for OA to counteract the inhibitory effect exerted by cycloheximide on the induction of GVBD and activation of histone H1 kinase in the absence of FSH, whereas this first culture period was prolonged for 2 h in the presence of FSH. Furthermore, even in FSH-stimulated oocytes, H-8 facilitated an OA-counteracted overcome of the cycloheximide-dependent GVBD block after 2 h of initial culture for protein synthesis. From these results, it is concluded that cAMP-dependent protein kinase activity regulated by cumulus cells following FSH-stimulation requests plays a role in the complex mechanism of chromatin condensation and MPF activation leading to meiotic resumption in bovine oocytes.

Animals↗

PubMed1982

Enzymatic condensation of nonassociated peptide fragments using a molecular trap.

We have tested the feasibility of achieving protease-catalyzed condensation between nonassociating peptide fragments through mediation of a molecular trap. In this study, two subfragments of bovine pancreatic ribonuclease S-peptide, containing residues 1-10 and 11-15, were rejoined by clostripain catalysis to form the 1-15 peptide. The extent of this stereospecific condensation was enhanced by adding ribonuclease S-protein (residues 21-124), which acts as a trap in binding 1-15 but not 1-10 or 11-15 and which thus shifts the equilibrium to favor 1-15 formation. The resultant (1-15) X (21-124) noncovalent complex, defined as [des-16-20]ribonuclease S, was detected by the enzymatic activity characteristic of the naturally derived ribonuclease S complex. Reaction of 1 mM S-protein and 20 mM fragments leads to 80% of the ribonuclease activity expected from the amount of 21-124 present. This indicates that 4% of the fragments 1-10 and 11-15 were condensed, compared to a maximal condensation of 5% based on the amount of trap. The less than theoretical yield is due largely to slow proteolytic degradation of 21-124 to a form which is no longer able to bind the condensation product 1-15. Yields were increased to 15% by addition of further trap. The successful synthesis of 1-15 emphasizes the usefulness of molecular traps to promote stereospecific fragment condensation between nonassociating peptide fragments for the synthesis and semisynthesis of polypeptides.

Amino Acids↗