Flow cytometric resonance energy transfer measurements support the association of a 95-kDa peptide termed T27 with the 55-kDa Tac peptide.

Two monoclonal antibodies (OKT27 and OKT27b) have been produced that react with distinct epitopes of a 95-kDa peptide. The T27 antigen is widely distributed, being expressed on B lymphocytes, monocytes, and adult T-leukemic cells but not on polymorphonuclear leukocytes or platelets. There was a low level of T27 expression on resting T cells that increased on T-cell activation. In preliminary studies, the OKT27b antibody coprecipitated a 55-kDa peptide, as well as the 95-kDa peptide, from the radiolabeled cells of the HuT 102B2 cell line. Preclearance with anti-Tac, a monoclonal antibody to the 55-kDa peptide of the multichain interleukin 2 receptor, removed the 55-kDa but not the 95-kDa peptide from subsequent OKT27b immunoprecipitates of HuT 102B2 extracts, suggesting the possibility that the T27 peptide was associated with the Tac peptide. However, the precipitation of the p55 Tac peptide by OKT27b was quite inconsistent. Thus, additional information was sought using a flow cytometric energy transfer technique to provide a physical estimation of the proximity between the Tac and the T27 peptides. The flow cytometric version of the fluorescence resonance energy transfer technique permits the determination of inter- and intramolecular distances at 2- to 10-nm levels on a cell-by-cell basis. Using this approach, there was a mean energy transfer of 7.3% with HuT 102B2 cells when fluorescein isothiocyanate anti-Tac served as the donor and tetramethylrhodamine isothiocyanate OKT27 served as the acceptor. In contrast, there was no energy transfer in comparable studies observed when fluorescein anti-Tac and rhodamine anti-transferrin receptor antibodies were used. These observations support the conclusion that there is a close nonrandom proximity in HuT 102B2 cells between the 95-kDa peptide identified by the OKT27 monoclonal antibody and the p55 Tac peptide of the multichain interleukin 2 receptor.

Physicochemical and biological comparison of polyene macrolide antibiotics fungichromin, lagosin and cogomycin.

The three polyene macrolide antibiotics, fungichromin, lagosin, and cogomycin, previously described as having some stereochemical differences at one or more centers, are shown by countercurrent distribution, high-performance liquid chromatography, carbon-13 nuclear magnetic resonance spectroscopy, circular dichroism, and biological studies to be identical in all respects, including stereochemical aspects. The differences observed earlier in their properties have now been ascribed to varying amounts of impurities, which are separable by high-performance liquid chromatography. All three antibiotics contain one major and several minor components.

Fredericamycin A, a new antitumor antibiotic. I. Production, isolation and physicochemical properties.

A new antitumor antibiotic, fredericamycin A (FCRC-A48, NSC-305263), has been isolated from a strain of Streptomyces griseus (FCRC-48). Based on its unique ultraviolet-visible spectrum, infrared spectrum, proton and carbon-13 nuclear magnetic resonance spectra and mass spectra, it is judged to be a novel acid-base indicator type of compound. Its production, isolation and physicochemical properties are discussed. The isolation, ultraviolet-visible spectrum and some biological properties of two minor components, fredericamycin B and fredericamycin C, are also described.

Field desorption mass spectrometry in structural studies of polyene macrolide antibiotics: isolation and early identification of a pentaene macrolide antibiotic.

Isolation of a pentaene macrolide antibiotic (NSC-277813) from Streptomyces griseus (FCRC-21) fermentation broth is described. Using field desorption mass spectrometry and high resolution field desorption mass spectrometry on the intact and derivatized antibiotic and degradation products, the antibiotic was identified as fungichromin. The application of field desorption mass spectrometry in the identification of polyene antibiotics is discussed.

Isolation and structure elucidation of a novel griseorhodin.

Three antibiotics possessing cytotoxic properties were isolated from a strain of Streptomyces griseus (FCRC-57). One was found to be identical with griseorhodin A. A second, FCRC-57-U, was found to be identical to griseorhodin C. FCRC-57-G is a new antibiotic structurally related to griseorhodins A and C, and is active against KB cells in vitro. The structure of this new antibiotic was determined using mass spectrometry, proton and carbon nuclear magnetic resonance spectroscopy and synthesis.

Microbial reduction of the side-chain carbonyl of daunorubicin and N-acetyldaunorubicin.

Microorganisms reduced the side-chain carbonyl of daunorubicin to yield 13-dihydrodaunorubicin (daunorubicinol; daunomycinol). This microbial transformation occurred under aerobic conditions in agitated baffled shake flasks incubated at 37 degrees C. The microorganisms were first grown in a medium which supported dense growth. Daunorubicin-HCl was then added. Following a period of incubation, broths were adjusted to pH 10.0 and extracted with chloroform. Daunorubicinol was recovered and purified from the chloroform extracts by preparative TLC. Identity of the daunorubicinol was established by TLC and spectroscopy (UV-vis, IR, NMR, MS, CD and ORD). N-Acetyldaunorubicin was likewise reduced microbially to N-acetyldaunorubicinol. N-Acetyldaunorubicinol appears to be a new compound which is yet to be tested for antitumor activity.

Mass spectrometry of N-acylated daunorubicin derivatives.

The mass spectra of peracetylated daunorubicin, N-octanoyl-, N-dodecanoyl- and N-(N'-dodecanoyl-glycyl)daunorubicin, and perdeuteroacetylated N-dodecanoyldaunorubicin were analyzed. Major fragmentation pathways were suggested and ion compositions were determined by high resolution measurements.