Clinical use of single-dose surfactant TA therapy for premature infants with severe respiratory distress syndrome

A single dose of surfactant TA was given as rescue therapy to four small premature infants with severe respiratory distress syndrome requiring mechanical ventilation. Birth weights ranged from 810 to 1200 gm. The dose of 100-120 mg/kg was given at the mean age of 5 hours, with range of 3 to 7 hours. Following surfactant therapy, there was a significant improvement (p < 0.05) in a/APO2 (raising from 0.11 +/- 0.05 before treatment to 0.34 +/- 0.19 at 6 hours after treatment). There was also a significant reduction in the severity of respiratory distress syndrome at 24 hours post-therapy. One baby died of sepsis at 40 hours of life; one survived without complications. The other two cases developed severe bronchopulmonary dysplasia later. We concluded that early use of exogenous surfactant is beneficial in small premature infants with severe respiratory distress syndrome.

[Clinical and scanning electron microscopic studies on Norwegian scabies infection]

Two typical cases of Norwegian scabies were studied clinically, scanning electron microscopically and histopathologically. Case 1 was a boy with Down's syndrome and case 2 was a man with adult T cell leukemia/lymphoma. Their clinical pictures showed hyperkeratotic plaques and warty crusts on hands, feet, ears, elbows and buttocks. Direct examination of the KOH preparation revealed many embryonated sarcoptic eggs, postpartum egg-shells, fecal pellets, larvae and male and female adult mites. Histopathologic examination showed several burrows inside the thick horny layer. Many sarcoptic egg-shells, mites and fecal pellets were found in the burrows. Psoriasiform hyperplasia and parakeratosis were noted, too. The size and shape of the sarcoptic eggs and the detailed structure of mites and molt were observed by using a scanning electron microscope. Besides, hook-like structures were noted at the tarsi of both forelegs and hindlegs. We suggest that the larvae crawl out from longitudinal openings in the egg-shell by the use of hook-like structures. The mites also used these hook-like structures to make the burrows. Scanning electron microscopy provides a good method to understand the dynamics of these burrowing parasites. It is helpful in illustrating the behavior of the scabies mites in their burrows in Norwegian scabies patients.

A universal T cell epitope-containing peptide from hepatitis B surface antigen can enhance antibody specific for HIV gp120

Peptide-based vaccines that directly target T cell or B cell epitopes may have significant advantages over conventional vaccines. Further, synthetic chimeric peptides that combine strong T cell epitopes with poorly immunogenic, but immunodominant, B cell epitopes or strain-conserved B cell epitopes may be useful in eliciting antibody to such important regions. Here we characterize a human T cell epitope analyzed in 54 individuals immunized with a hepatitis B virus surface Ag vaccine. Primary cultures from a total of 59 immunized donors were assessed for their ability to respond to hepatitis B virus surface Ag and peptides, and five were non-responders (8.5%). T cell lines were established from the remaining 54 responders. Of the responders, it was found that the peptide representing amino acids 19 through 33 (19-33) elicited significant proliferation in lines derived from 50 donors. This "universal" T cell epitope, which was recognized in donors of many different HLA-DR and -DQ haplotypes, was then used to construct a chimeric peptide containing 19-33 and the third V region loop structure (V3 loop) of HIV-1 envelope gp 120, in an attempt to augment the immune response to the V3 loop peptide. The V3 loop is the region to which significant neutralizing antibody is directed. Thus, a strong immune response to a synthetic peptide that contains the strain-conserved V3 loop region could have significant therapeutic implications. The V3 loop/19-33 peptide was then used to prime mice, to determine whether V3 loop-specific antibody could be induced. The peptide elicited potent 19-33-specific proliferation in T cells isolated from draining lymph nodes, and in six of six mice anti-V3 loop antibody was elicited. Further, V3 loop/19-33-primed animals made significant levels of antibody that bound rgp120. These data suggest that, when a major T cell epitope is synthesized in tandem with the V3 loop, a significant immune response against the loop can be elicited. Thus, given the finding that neutralizing antibody may play a role in the control and/or prevention of HIV infection, an HIV vaccine composed of a T cell epitope-containing peptide may prove effective. In addition, this type of approach can be generalized to the design of peptide-based vaccines.

A universal T cell epitope-containing peptide from hepatitis B surface antigen can enhance antibody specific for HIV gp120

Peptide-based vaccines that directly target T cell or B cell epitopes may have significant advantages over conventional vaccines. Further, synthetic chimeric peptides that combine strong T cell epitopes with poorly immunogenic, but immunodominant, B cell epitopes or strain-conserved B cell epitopes may be useful in eliciting antibody to such important regions. Here we characterize a human T cell epitope analyzed in 54 individuals immunized with a hepatitis B virus surface Ag vaccine. Primary cultures from a total of 59 immunized donors were assessed for their ability to respond to hepatitis B virus surface Ag and peptides, and five were non-responders (8.5%). T cell lines were established from the remaining 54 responders. Of the responders, it was found that the peptide representing amino acids 19 through 33 (19-33) elicited significant proliferation in lines derived from 50 donors. This "universal" T cell epitope, which was recognized in donors of many different HLA-DR and -DQ haplotypes, was then used to construct a chimeric peptide containing 19-33 and the third V region loop structure (V3 loop) of HIV-1 envelope gp 120, in an attempt to augment the immune response to the V3 loop peptide. The V3 loop is the region to which significant neutralizing antibody is directed. Thus, a strong immune response to a synthetic peptide that contains the strain-conserved V3 loop region could have significant therapeutic implications. The V3 loop/19-33 peptide was then used to prime mice, to determine whether V3 loop-specific antibody could be induced. The peptide elicited potent 19-33-specific proliferation in T cells isolated from draining lymph nodes, and in six of six mice anti-V3 loop antibody was elicited. Further, V3 loop/19-33-primed animals made significant levels of antibody that bound rgp120. These data suggest that, when a major T cell epitope is synthesized in tandem with the V3 loop, a significant immune response against the loop can be elicited. Thus, given the finding that neutralizing antibody may play a role in the control and/or prevention of HIV infection, an HIV vaccine composed of a T cell epitope-containing peptide may prove effective. In addition, this type of approach can be generalized to the design of peptide-based vaccines.

Cytotoxic T lymphocytes from HIV-1 seropositive individuals recognize immunodominant epitopes in Gp160 and reverse transcriptase

The CTL response to HIV-1 is more vigorous than for any known human pathogen and may be a significant factor in preventing the progression to symptomatic disease. T cell lines, generated by non-specific stimulation with PHA and IL-2, may be reproducibly used to identify HIV-1 isolate-invariant epitopes recognized by the CTL of infected individuals. The CTL response in each of 12 infected individuals to envelope and reverse transcriptase (RT) is dominated by the recognition of one or two viral isolate-invariant epitopes. Seven subjects respond to a single gp160 epitope; three subjects recognize 2 gp160 epitopes. There is a significant increase in recognition of epitopes in the C terminal 104 amino acids of gp41 (p less than 0.002); in fact 40% of the subjects that respond to gp160 recognize the C terminal 20-mer. The CTL-mediated lysis of gp160-expressing targets is MHC restricted, but not all individuals that share the same serologically defined class I-restricting element respond to the same epitope. Recognition of the terminal 20mer is restricted by both A30 and B8. The response to RT in six subjects is distributed over the RT protein. The six subjects recognize four separate regions defined by truncated RT-vaccinia recombinants, but none of the subjects' CTL demonstrate significant recognition of the RT epitope identified in H-2k mice and some humans.

Cytotoxic T lymphocytes from HIV-1 seropositive individuals recognize immunodominant epitopes in Gp160 and reverse transcriptase

The CTL response to HIV-1 is more vigorous than for any known human pathogen and may be a significant factor in preventing the progression to symptomatic disease. T cell lines, generated by non-specific stimulation with PHA and IL-2, may be reproducibly used to identify HIV-1 isolate-invariant epitopes recognized by the CTL of infected individuals. The CTL response in each of 12 infected individuals to envelope and reverse transcriptase (RT) is dominated by the recognition of one or two viral isolate-invariant epitopes. Seven subjects respond to a single gp160 epitope; three subjects recognize 2 gp160 epitopes. There is a significant increase in recognition of epitopes in the C terminal 104 amino acids of gp41 (p less than 0.002); in fact 40% of the subjects that respond to gp160 recognize the C terminal 20-mer. The CTL-mediated lysis of gp160-expressing targets is MHC restricted, but not all individuals that share the same serologically defined class I-restricting element respond to the same epitope. Recognition of the terminal 20mer is restricted by both A30 and B8. The response to RT in six subjects is distributed over the RT protein. The six subjects recognize four separate regions defined by truncated RT-vaccinia recombinants, but none of the subjects' CTL demonstrate significant recognition of the RT epitope identified in H-2k mice and some humans.

Amino acid sequence of Fel dI, the major allergen of the domestic cat: protein sequence analysis and cDNA cloning

The complete primary structure of Fel dI (International Union of Immunological Societies nomenclature), the major allergen produced by the domestic cat, Felis domesticus, was determined by protein sequence analysis and cDNA cloning. Protein sequencing of Fel dI from an immunoaffinity-purified extract of house dust revealed that the allergen is composed of two polypeptide chains. Degenerate oligonucleotides derived from the protein sequence were used in polymerase chain reaction amplification of cat salivary gland cDNA to demonstrate that the two chains are encoded by different genes. Chain 1 of Fel dI shares amino acid homology with rabbit uteroglobin, while chain 2 is a glycoprotein with N-linked oligosaccharides.

Complete sequence of the allergen Amb alpha II. Recombinant expression and reactivity with T cells from ragweed allergic patients

This study defines the complete primary structure of Amb alpha II, an important allergen produced by short ragweed (Ambrosia artemisiifolia). The deduced amino acid sequence derived from the cDNA indicates that Amb alpha II shares approximately 65% sequence identity with the Amb alpha I multigene family of allergens. Full-length cDNA encoding Amb alpha I.1 and Amb alpha II have been expressed in E. coli and purified. An in-frame linker encoding polyhistidine has been added to the 5' end of the cDNA to facilitate purification using Ni2+ ion affinity chromatography, yielding greater than 90% pure recombinant protein in a single step. T cells from patients allergic to ragweed proliferate in response to pollen extract as well as purified recombinant Amb alpha I.1 and Amb alpha II. T cell lines established using either Amb alpha I.1 or II as the stimulating Ag exhibit a high level of cross-reactivity to both proteins. This result is entirely consistent with the extensive primary sequence identity shared by these two proteins. These data suggest that allergic humans recognize shared T cell epitopes on these two related molecules.

Complete sequence of the allergen Amb alpha II. Recombinant expression and reactivity with T cells from ragweed allergic patients

This study defines the complete primary structure of Amb alpha II, an important allergen produced by short ragweed (Ambrosia artemisiifolia). The deduced amino acid sequence derived from the cDNA indicates that Amb alpha II shares approximately 65% sequence identity with the Amb alpha I multigene family of allergens. Full-length cDNA encoding Amb alpha I.1 and Amb alpha II have been expressed in E. coli and purified. An in-frame linker encoding polyhistidine has been added to the 5' end of the cDNA to facilitate purification using Ni2+ ion affinity chromatography, yielding greater than 90% pure recombinant protein in a single step. T cells from patients allergic to ragweed proliferate in response to pollen extract as well as purified recombinant Amb alpha I.1 and Amb alpha II. T cell lines established using either Amb alpha I.1 or II as the stimulating Ag exhibit a high level of cross-reactivity to both proteins. This result is entirely consistent with the extensive primary sequence identity shared by these two proteins. These data suggest that allergic humans recognize shared T cell epitopes on these two related molecules.

Cloning of Amb a I (antigen E), the major allergen family of short ragweed pollen

To determine the structure of Amb a I (previously called antigen E), the major allergen from short ragweed, cDNA from pollen was cloned into lambda gt11 and lambda gt10. One of the three distinct clones isolated from the lambda gt11 library by screening with anti-denatured Amb a I antibodies was used to screen both libraries for other Amb a I sequences. Multiple clones were isolated and sequenced and proved to be highly homologous but nonidentical. The clones could be divided into three groups based on sequence similarity, and in accordance with the International Union of Immunological Societies-approved nomenclature (Marsh, D. G., Goodfriend, L., King, T. P., Lowenstein, H., and Platts-Mills, T. A. E. (1986) Bull. WHO 64, 767-770) they have been designated Amb a I.1, Amb a I.2, and Amb a I.3. Clones within a group have greater than 99% identity, and similarity among groups is 85-90% at the nucleotide level. The amino acid sequence of four peptides (isolated from antigen E obtained from the Research Resources Branch of the National Institutes of Health) containing 132 amino acids was identical to one of the clones (Amb a I.1). The presence of multiple naturally occurring isoelectric forms of Amb a I was demonstrated by two-dimensional gel electrophoresis and Western blotting. Southern blot analysis demonstrates the presence of multiple Amb a I-related sequences in the ragweed genome. Amb a I is therefore not a single molecule but rather a family of closely related proteins.

Energy absorption, lean body mass, and total body fat changes during 5 weeks of continuous bed rest

Inactivity causes profound changes. We determined the nature of the body composition changes due to inactivity, and sought to determine if these changes are secondary to changes in energy absorption. Volunteers were 15 healthy males who lived on a metabolic research ward under close staff supervision for 11 weeks. Subjects were ambulatory during the first 6 weeks and remained in continuous bed rest for the last 5 weeks of the study. Six male volunteers (age 24-61 years, height 175.7 +/- 4.2 cm) were selected for body composition measurements. Nine different male volunteers (age 21-50 years, height 177.7 +/- 5.0 cm) were selected for energy absorption measurements. The volunteers were fed weighed conventional foods on a constant 7-d rotation menu. The average daily caloric content was 2,592 kcal. Comparing the 5 weeks of continuous bed rest with the previous 6 weeks of ambulation we observed: no change in energy absorption or total body weight during bed rest, but a significant decrease in lean body mass and a significant increase in total body fat (p less than 0.05).

Structural nature of the interaction between T lymphocyte surface molecule CD4 and the intracellular protein tyrosine kinase lck

The strong non-covalent interactions between T lymphocyte surface CD4 or CD8 molecules and the intracellular membrane-associated protein tyrosine kinase lck are likely to mediate the role of CD4 and CD8 molecules in the immune response. The delineation of the structural nature of the CD4/lck and CD8/lck complexes is important for the understanding of the biochemical and functional significance of the interactions. Complementary charged regions in the C-terminal intracytoplasmic portions of CD4 or CD8, and in the N-terminal region of protein tyrosine kinase lck were noted. Peptides spanning these regions, residues 417 to 429 of CD4 and 10 to 22 of lck, were found to specifically dissociate these two molecules in CD4/lck complexes. A structural model of the interaction that accounts for its high stability is proposed.

Rabbit-mouse hybridomas secreting intact rabbit immunoglobulin

Rabbit-mouse hybridomas offer the potential for production of monoclonal rabbit antibodies by immortal cell lines. In previous studies, it was possible to produce and stabilize rabbit-mouse hybrid cells secreting either a rabbit heavy or light chain. These have been useful for structural characterization of the individual rabbit immunoglobulin polypeptides and for isolation of large amounts of immunoglobulin mRNA for molecular studies. For some studies, however, it would be useful to have intact rabbit immunoglobulin molecules comparable to the myeloma proteins available in the human and mouse. The availability of rapid, sensitive and specific assays for rabbit heavy and light chains and allotypes located on specific chains has now permitted the early identification of clones secreting intact rabbit immunoglobulin. Vigorous cloning efforts have resulted in isolation and partial stabilization of three such clones. The first, H105, secretes a product with a kappa light chain bearing the b6 allotype and a mu-chain bearing the a1 allotype. Biochemical and serologic analyses of the product show that it is secreted as a fully assembled IgM pentamer and that the rabbit heavy and light chains are covalently associated. No rabbit J-chain gene was detected in H105 by Southern blot analysis. The second hydridoma, H134, secretes a product with a mol. wt of 150 K, consisting of a b4 light chain and an a1 heavy chain. The third, H171, secretes an alb4 IgG with antibody specificity for group C streptococcal carbohydrate. An additional rabbit-mouse hybridoma, H89, have been produced which secretes a rabbit heavy chain lacking group a allotypic activity. The rabbit heavy chain, which is associated with a mouse light chain, has an N-terminal amino acid sequence identical to a2-positive molecules although thorough serologic analysis revealed no group a allotypic activity.

The detection of HLA-DR, MB and MT determinants on purified class II molecules by inhibition of microcytotoxicity

An assay has been developed which makes it possible to determine the HLA allospecificities carried by molecules in purified fractions of detergent lysates from EBV-transformed human lymphocytes. It is based on inhibition of the standard microlymphocytotoxic test used for identifying HLA class I and II antigens with alloantisera. Soluble cell membrane products from EBV-transformed cell lines homozygous for the HLA region gave specific inhibition of standard typing antisera. The test requires preincubation of microliter volumes of soluble antigen preparations maintained in 0.05% NP-40 with selected antisera prior to adding EBV-transformed cells as target cells. It was possible using this assay to follow isolation of the structurally related human class II molecules bearing the MB and DR specificities. Detergent lysates of cells were fractionated on affinity columns prepared from monoclonal antibodies directed against distinct class II antigens. Eluates from these columns contained the expected DR and MB specificities. The assay is easy to perform, highly reproducible and allows multiple determinations.

Primary structural sequence polymorphism in the human class II MHC antigen 33.1

Monoclonal antibody 33.1 defines a non-DR, class II, human major histocompatibility complex antigen, 33.1, which appears to be distinct from other class II antigens in its cellular distribution and primary structure. To characterize the structure more fully and to determine the degree of polymorphism within 33.1, a comparative N-terminal sequence study has been undertaken using a series of ten B lymphoblastoid cell lines with different DR and MB types. The results confirm that both the alpha and beta chains of 33.1 are homologues of the corresponding chains of the murine I-A antigen and indicate that while 33.1 does not appear to be identical with MB, it is closely related. Sequence analyses revealed two major variants of 33.1, corresponding to cells with specificities MB1 and MB3, respectively. Within each MB type, other polymorphisms have been detected. Cells that are MB2 do not react with monoclonal antibody 33.1. Suggestive evidence is presented that monoclonal antibody 33.1 reacts predominantly with the beta chain of the antigen. The preferential expression of 33.1 on activated B cells suggests that expression of at least the 33.1 beta chain gene is greatly enhanced in the course of B-cell activation, but the specific function of 33.1 remains to be determined.

A novel HLA-D/DR-like antigen specific for human B lymphoid cells. Biochemical evidence for similarity to but nonidentity with known HLA-D/DR antigens

The polymorphic human B cell-specific antigen, 33.1, detected by a murine monoclonal antibody, was compared by genetics and structural analysis with known human Ia antigens from a panel of DR homozygous Epstein-Barr virus-transformed B lymphoblastoid cell lines. Cells homozygous for DR 1, 2, 4, 5, and w6 were positive, while cells that are DR3,3 or DR7,7 usually failed to express this antigen. Mutant DR null, DC/MB-positive cells were 33.1 positive while DR null, DC/MB-negative cells failed to express this antigen, suggesting the segregation of 33.1 with the DC antigen. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that 33.1 alpha and beta chains were of lower molecular weights than the DR alpha and beta chains isolated from the same cell line. Partial N-terminal amino acid sequence analyses were carried out for the heavy and light chains of the 33.1 antigen radiolabeled with [3H] phenylalanine. The results of these analyses, in conjunction with previous data on tissue distribution, indicate that the 33.1 antigen is a non-DR but Ia-like antigen closely related to the previously defined I-A homologues, DC and DS.

Allotype-defined mRNA for rabbit immunoglobulin H and L chains isolated from rabbit-mouse hybridomas

Improved procedures have expedited the formation and propagation of stable rabbit-mouse hybridomas (RMH) that secrete rabbit immunoglobulin (Ig) chains and that serve as sources for allotype-defined mRNA, specifying both constant and variable regions of rabbit Ig. The Ig-secreting hybridomas were stabilized by multiple recloning steps and eventually attained a 90% frequency of cells secreting rabbit Ig chains. Stabilized RMH were propagated in vivo in nude (athymic) and in some instances in conventional BALB/c mice. Rabbit Ig products secreted by these RMH cell lines were isolated and were shown to have amino acid sequence characteristics of rabbit Ig chains and that are distinct from those of the mouse. Preparative amounts of polyadenylated RNA-(poly(A) RNA) encoding allotype-defined rabbit Ig chains were isolated from RMH grown as solid tumors. Poly(A) RNA encoding a b4 L chain from one RMH (12F2) and an a3 H chain from another (7D2) were purified 10-fold by sucrose density gradient centrifugation and were characterized in an in vitro translation system. The mRNA encoding the b4 allotype had an S value of 12 and directed the synthesis of a rabbit precursor L chain with m.w. 27,500. Radiochemical amino acid sequence analysis of the L chain precursor has shown it to include a 22 residue leader sequence with a leucine profile similar to that of murine L chain precursors. Analysis of the mRNA encoding the a3 H chain revealed it has an S value of 16 and directed the synthesis of an Ig chain with a m.w. identical to that of the rabbit H chain secreted by the RMH.

Allotype-defined mRNA for rabbit immunoglobulin H and L chains isolated from rabbit-mouse hybridomas

Improved procedures have expedited the formation and propagation of stable rabbit-mouse hybridomas (RMH) that secrete rabbit immunoglobulin (Ig) chains and that serve as sources for allotype-defined mRNA, specifying both constant and variable regions of rabbit Ig. The Ig-secreting hybridomas were stabilized by multiple recloning steps and eventually attained a 90% frequency of cells secreting rabbit Ig chains. Stabilized RMH were propagated in vivo in nude (athymic) and in some instances in conventional BALB/c mice. Rabbit Ig products secreted by these RMH cell lines were isolated and were shown to have amino acid sequence characteristics of rabbit Ig chains and that are distinct from those of the mouse. Preparative amounts of polyadenylated RNA-(poly(A) RNA) encoding allotype-defined rabbit Ig chains were isolated from RMH grown as solid tumors. Poly(A) RNA encoding a b4 L chain from one RMH (12F2) and an a3 H chain from another (7D2) were purified 10-fold by sucrose density gradient centrifugation and were characterized in an in vitro translation system. The mRNA encoding the b4 allotype had an S value of 12 and directed the synthesis of a rabbit precursor L chain with m.w. 27,500. Radiochemical amino acid sequence analysis of the L chain precursor has shown it to include a 22 residue leader sequence with a leucine profile similar to that of murine L chain precursors. Analysis of the mRNA encoding the a3 H chain revealed it has an S value of 16 and directed the synthesis of an Ig chain with a m.w. identical to that of the rabbit H chain secreted by the RMH.

Linking a bloodstain to a missing person by genetic inheritance

The use of the principles of genetic inheritance to link a bloodstain to a missing victim is discussed. Genetic marker typing can determine whether the parents of the missing victim are possible parents of the bloodstain source. Given a parental inclusion, it is possible to calculate the probability that a randomly selected couple would possess the necessary genetic combinations to be the parents of the person who bled. The applications of this concept using several genetic marker systems are examined. General formulas have been developed for the probability calculation using phenotype distribution frequencies and gene frequencies. This approach was applied to a homicide case in which it was shown that the victim's parents were among only 0.8% of couples from the general population who would be able to bequeath the genetic marker types found in the bloodstain. This evidence was helpful in producing a conviction of first degree murder.

Nuclear Overhauser effect and cross-relaxation rate determinations of dihedral and transannular interproton distances in the decapeptide tyrocidine A

The following interproton distances are reported for the decapeptide tyrocidine A in solution: (a) r(phi) distances between NH(i) and H alpha (i), (b) r(psi) distances between NH (i + 1) and H alpha (i), (c) r(phi psi) distances between NH(i + 1) and NH(i), (d) NH in equilibrium NH transannular distances, (e) H alpha in equilibrium H alpha transannular distances, (f) r x 1 distances between H alpha and H beta protons, (g) NH(i) in equilibrium H beta (i) distances, (h) NH (i + 1) in equilibrium H beta (i) distances, (i) carboxamide-backbone protons and carboxamide-side chain proton distances, (j) side chain proton-side chain proton distances. The procedures for distance calculations were: NOE ratios and calibration distances, sigma ratios and calibration distances, and correlation times and sigma parameters. The cross-relaxation parameters were obtained from the product, say, of NOE 1 leads to 2 and the monoselective relaxation rate of proton 2; the NOEs were measured by NOE difference spectroscopy. The data are consistent with a type I beta-turn/ type II' beta-turn/ approximately antiparallel beta-pleated sheet conformation of tyrocidine A in solution and the NOEs, cross-relaxation parameters, and interproton distances serve as distinguishing criteria for beta-turn and beta-pleated sheet conformations. It should be borne in mind that measurement of only r phi and r psi distances for a decapeptide only defines the ( phi, psi)-space in terms of 4(10) possible conformations; the distances b-j served to reduce the degeneracy in possible (phi, psi)-space to one tyrocidine A conformation. The latter conformation is consistent with that derived from scalar coupling constants, hydrogen bonding studies, and proton-chromophore distance measurement, and closely resembles the conformation of gramicidin S.

Determination of individual side-chain conformations, tertiary conformations, and molecular topography of tyrocidine A from scalar coupling constants and chemical shifts

We report for the decapeptide tyrocidine A: (a) H alpha and H beta chemical shifts and scalar coupling constants for most residues of tyrocidine A in methanol-d4 and dimethyl-d6 sulfoxide (Me2so-d6) and the H alpha and H beta chemical shifts for other residues; (b) scalar coupling constants 3J alpha beta for nine side chains in methanol-d4 but only seven side chains in Me2SO-d6, due to chemical shift degeneracy; the Gln9 and Tyr10 side chains in methanol-d4 were only approximately analyzed; (c) a total spin-spin analysis of Pro5 in Me2SO-d6 and, partly by comparison, also in methanol-d4; (d) conversion of 3J alpha beta values to side-chain conformations for all residues in methanol-d4; comparisons, where possible, led to the conclusion that side-chain conformations are similar in methanol-d4 and Me2SO-d6; (e) an absolute conformational analysis of Pro5 from 3J values and a method of assigning all pro-R,S protons; Pro5 has a Ramachandran B, C2-Cexo-Cendo conformation; (f) chi 1, chi 2 conformations of several aromatic residues based upon proton-chromophore distance measurement from anomalous chemical shifts and Johnson-Bovey diagrams; (g) pro-R and pro-S assignments of H beta's from anomalous chemical shifts, high-temperature dependence of anomalous chemical shifts, and backbone side-chain nuclear Overhauser effects; (h) most tertiary conformations of the whole tyrocidine A molecule possessing residues 4--8 and 10 in highly preferred (ca. 90%) chi 1 conformations, but residues 1--3 and 9 having at least two chi 1 rotamers; (2) description of three topographical regions of the molecule--a hydrophobic region, a flat hydrophilic surface on the other side of the molecule, and a hydrophilic region consisting of two peptide backbone units and the side chains of Asn8, Gln9, and Tyr10; (j) proposed side chain, beta-turn, and beta-pleated sheet conformations that readily account for all "normal" and anomalous chemical shifts.