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S Natarajan

Publications and source records attributed to S Natarajan.

124 records · Page 7Linked to original sources
PubMed1977

Ring formation in a pentapeptide with alternating L and D residues: an analogy to cyclization in the biosynthesis of peptide antibiotics.

Acetylation of L-isoleucyl-D-alanyl-D-alanyl-L-valyl-D-leucine with acetic anhydride followed by methylation with diazomethane yielded the expected acetylpentapeptide methyl ester with molecular weight 541, but also resulted in the formation of a by-product with molecular weight 555. The incorporation of the mass corresponding to CH2 seems to be due to ring closure--via a mixed anhydride--and methylation of the cyclol derivative thus formed. A preferred, ring-like conformation stabilized by intramolecular hydrogen bonds that in turn are the consequences of the alternation of D- and L- residues in the sequence, is invoked as explanation for the unexpected cyclization. This assumption is supported by the conversion of the pentapeptide methyl ester to desthiomalformain in molten imidazole.

Acetylation↗
PubMed1976

High resolution mass spectra of malformin and related cyclic peptides.

A comparison of the high resolution mass spectra of synthetic and natural preparations of malformin provided new evidence for the revised structure: (see article): The interpretation of the mass spectra was aided by the examination of the spectra of the synthetic peptides, desthiomalformin and enantio-5-valine malformin.

Disulfides↗
PubMedDate not supplied

Antiovulatory antagonists of LHRH related to antide.

We report 104 analogues of the potent antiovulatory antagonist of LHRH, N-Ac-D-Nal-D-Cpa-D-Pal-Ser-Lys(Nic)-D-Lys(Nic)-Leu-Ilys-Pro-D-Ala- NH2, Antide. We replaced the Nic group in Antide with other acyl substituents to modulate size, hydrophilicity or basicity of the molecule, we also replaced the Lys residues with shorter basic amino acids, and made cyclic 5/6 analogues as well as position 5 or 6 dimers. We substituted Ilys8 with other alkyl groups and acyl derivatives. When injected in 0.1% DMSO in water in a typical antiovulatory (AO) assay. Antide gives six rats ovulating out of eight (6/8) at 2 micrograms, 4/8 at 4 micrograms, and in the histamine release assay (HRA). ED50 is > 300 micrograms/ml; [Lys(N-Isobutyl)8]Antide gave 2/8 at 2 micrograms/rat; [Lys (8-Qis)5]Antide gave 1/8 at 1 microgram, and 0/8 at 2 micrograms, and in the HRA ED50. 22 micrograms/ml; [D-Lys(8-Qis)5]Antide gave 4/8 at 1 microgram and 0/8 at 2 micrograms, and in the HRA, ED50 was 27 micrograms/ml; [Lys(8-Qic)8] gave 5/8 at 1 microgram 1/8 at 2 micrograms/ [Lys(2-Pyc)6]Antide gave 3/8 at 1 microgram, and 0/8 at 2 micrograms, and in the HRA ED50 was 116 micrograms/ml; [D-Lys (2-Pyc)5]Antide gave 5/8 at 1 microgram and in the HRA, ED50 was 100- > 300 micrograms/ml; [Lys(2-Pyc)5.D-Lys(2-Pyc)6]Antide gave 2/8 at 1 microgram. The substitutions of the Nic groups of Antide at Lys5 or D-Lys6 with 8-Qis or with 2-Pyc groups seem to give highly potent antiovulatory antagonists of LHRH and constitute significant new leads to generate potent antiovulatory compounds endowed with moderate or low histamine release.

Amino Acid Sequence↗
PubMedDate not supplied

Transient myeloproliferative disorder in Down syndrome presenting with ascites: a case report.

BACKGROUND: An increased frequency of acute myelogenous leukemia is a well known feature in children with Down syndrome. In addition, transient myeloproliferative disorders (TMD), which may mimic acute leukemia, also occur in neonates with Down syndrome. TMD is recognized shortly after birth or in the neonatal period and is characterized by leukocytosis and thrombocytopenia, which resolve spontaneously in four to six weeks. CASE: A 1.5-month-old, male infant born with Down syndrome and patent ductus arteriosus presented with abdominal distention due to ascites. Cytology of the fluid revealed immature myeloid cells and megakaryocytes. Flow cytometry of the ascitic fluid confirmed the presence of immature myelomonocytic cells. A complete hematologic evaluation along with the clinical findings supported the diagnosis of TMD in Down syndrome. CONCLUSION: TMD is an uncommon syndrome strongly associated with Down syndrome. Since the abnormal laboratory findings are seen primarily in the peripheral blood, it is usually diagnosed by a hematopathologist without much difficulty. Our case demonstrates the importance of cytopathologist familiarity with this entity so as not to erroneously diagnose a leukemic process. This is extremely important since most cases of TMD spontaneously resolve within a few weeks to months and do not require treatment other than supportive measures.

Ascites↗
PubMedDate not supplied

Advances in wound care and healing technology.

Wounds are unique in so far as no disease process other than wounds would have existed from the beginning of mankind. Over the years, the management of wounds, especially that of chronic wounds, has had enormous social and economic implications worldwide. With an aging population, this impact is likely to increase. In recent years, this has been reflected by the birth and rapid growth of the new speciality of 'wound healing'. Continuous advances made in the study of the wound microenvironment, an ever-broadening understanding of the pathophysiology of wounds, and improved techniques in monitoring the response of healing have led to continuing developments in the treatment of chronic wounds. Current research focuses on growth factors and human skin substitutes that provide promising results. This article reviews advances made in wound care management over the years. Despite all these advances, it must be borne in mind that basic principles of wound care in a multidisciplinary team setting still remain the backbone of wound management.

Bandages↗