Conformational restrictions of peptides via backbone modification: Solution and crystal-state analysis of Boc-L-Pro-DZPhe-Gly-NH2

An N-alpha-protected model tripeptide amide containing, in the central position, an alpha,beta-dehydrophenylalanine (Z-configurational isomer), Boc-L-Pro-DELTA-Z-Phe-Gly-NH2 (Boc, tert-butyloxycarbonyl), has been synthesized by solution methods and fully characterized. IR absorption and H-1 NMR studies provided evidence for the occurrence of a significant population of a conformer containing two consecutive, intramolecularly H-bonded (type II-III') beta-bends in solution. However, an X-ray diffraction analysis clearly indicates that only the type-II beta-bend structure survives in the crystal state.

Acta Societatis pro fauna et flora Fennica

Kielet saksa ja ruotsi. Nimiösivulla teksti Helsingforsiae 1924-27.

Acta Societatis pro fauna et flora Fennica

Kielet saksa ja ruotsi. Nimiösivulla teksti Helsingforsiae 1924-29.

Acta Societatis pro fauna et flora Fennica

Kielet suomi ja saksa. Nimiösivulla teksti Helsingforsiae 1935-36.

Acta Societatis pro fauna et flora Fennica

Kielet saksa ja ruotsi.

Acta Societatis pro fauna et flora Fennica

Kielet saksa ja ruotsi.

Gender and female entrepreneurship in a pro-entrepreneurship magazine

In this working paper I discuss gendered entrepreneurship by exploring how the media writes about female entrepreneurship. The starting point is that the media when talking and writing about female entrepreneurs and female entrepreneurship, mould meanings of gender in entrepreneurship. I view entrepreneurship and gender as socially constructed, discursive phenomena. To uncover the processes of constructing gender in female entrepreneurship this paper applies a discursive framework, which treats language as a representational system producing and circulating meaning. The focus on language use as action implies that practises of writing and talking about female entrepreneurship ‘make’ gender as much as the women entrepreneurs) themselves: both involve working on culturally shared meanings to make reality intelligible. The data consists of articles published in Yrittäjä, a pro-SME magazine, in 1990-1997. In the analysis I show how gender is constructed in media talk. as a women’s issue Women entrepreneurs are constantly compared with men and with an implicitly masculine ideal of entrepreneurship and with strengths and weaknesses of women are displayed pointing out that the meaning making of gender taking place in the data refers to equality discourse. Finally I discuss possible consequences of the hegemonic equality discourse and suggest lines of further research.

Peptide hairpin nucleation with the obligatory Type I' beta-turn Aib-(D)Pro segment

The alpha-aminoisobutyric acid-D-proline (Aib-(D)Pro) dipeptide is an obligatory Type I' beta-turn forming segment that nucleates hairpin formation.

Conformations of peptides containing Z-alpha,beta-dehydroleucine (delta ZLeu). A comparison of Boc-Pro-delta ZLeu-Gly-NHEt and Boc-Pro-delta ZPhe-Gly-NHEt.

Two tripeptides of the type Boc-Pro-ΔZX-Gly-NHEt (where X = Leu, Phe) have been synthesized and their solution conformations investigated by 270 MHz 1H n.m.r. and i.r. spectroscopy. These conformational studies indicated that ΔZLeu, similar to ΔZPhe, has a strong tendency to stabilize folded Type II β-turn conformations when present at i + 2 position.

Stabilization of unusual structures in peptides using alpha,beta-dehydrophenylalanine: Crystal and solution structures of Boc-Pro-Delta Phe-Val-Delta Phe-Ala-OMe and Boc-Pro-Delta Phe-Gly-Delta Phe-Ala-OMe

The structures of two dehydropentapeptides, Boc-Pro-Delta Phe-Val-Delta Phe-Ala-OMe (I) and Boc-Pro-Delta Phe-Gly-Delta Phe-Ala-OMe (II) (Boc: t-butoxycarbonyl), have been determined by nuclear magnentic resonance (NMR), circular dichroism (CD), and X-ray, crystallographic studies. The peptide I assumes a S-shaped flat beta-bend structure, characterized by two partially overlapping type II beta-bends and absence of a second 1 <- 4 (N4-H center dot center dot center dot O1') intramolecular hydrogen bond. This is in contrast to the generally observed 3(10)-helical conformation in peptides with Delta Phe at alternate positions. This report describes the novel conformation assumed by peptide I and compares it with that of the conserved tip of the V3 loop of the HIV-1 envelope glycoprotein gp120 (sequence, G:P319 to F:P324, PDB code IACY). The tip of the V3 loop also assumes a S-shaped conformation with Arg:P322, making an intramolecular side-chain-backbone interaction with the carbonyl oxygen of Gly:P319. Interestingly, in peptide I, C(gamma)HVal(3) makes a similar side-chain-backbone C-H center dot center dot center dot O hydrogen bond with the carbonyl oxygen of the Boc group. The observed overall similarity indicates the possible use of the peptide as a viral antagonist or synthetic antigen. Peptide 11 adopts a unique turn followed by a 3(10)-helix. Both peptides I and II are classical examples of stabilization of unusual structures in oligopeptides.

Polypeptide models of collagen. II. Solution properties of (Pro-Gly-Phe)n

The conformation of (Pro-Gly-Phe)n in trifluoroethanol was investigated using CD, nmr and ir techniques. After making appropriate correction for the contribution of the phenylalanine chromophore to the observed CD spectra of the polytripeptide at several temperatures, it is found that (Pro-Gly-Phe)n can exist in a partially triple-helical conformation in this solvent a t low temperatures. The nmr and ir data support this conclusion. In conjunction with recent theoretical sutdies, our data offer an explanation for the preferential occurrence of the Phe residue in position 2 of the tripeptide sequence Gly-R2-R3, in collagen.

Diproline Templates as Folding Nuclei in Designed Peptides. Conformational Analysis of Synthetic Peptide Helices Containing Amino Terminal Pro-Pro Segments

The effect of N-terminal diproline segments in nucleating helical folding in designed peptides has been studied in two model sequences Piv-Pro-Pro-Aib-Leu-Aib-Phe-OMe (1) and Boc-Aib-Pro-Pro-Aib-Val-Ala-Phe-OMe (2). The structure of 1 in crystals, determined by X-ray diffraction, reveals a helical (RR) conformation for the segment residues 2 to 5, stabilized by one 4 -> 1 hydrogen bond and two 5 -> 1 interactions. The N-terminus residue, Pro(1) adopts a polyproline II (P-II) conformation. NMR studies in three different solvent systems support a conformation similar to that observed in crystals. In the apolar solvent CDCl3, NOE data favor the population of both completely helical and partially unfolded structures. In the former, the Pro-Pro segment adopts an alpha(R)-alpha(R) conformation, whereas in the latter, a P-II-alpha(R) structure is established. The conformational equilibrium shifts in favor of the P-II-alpha(R) structure in solvents like methanol and DMSO. A significant population of the Pro(1)- Pro(2) cis conformer is also observed. The NMR results are consistent with the population of at least three conformational states about Pro- Pro segment: trans alpha(R)-alpha(R), trans P-II-alpha(R) and cis P-II-alpha(R). Of these, the two trans conformers are in rapid dynamic exchange on the NMR time scale, whereas the interconversion between cis and trans form is slow. Similar results are obtained with peptide 2. Analysis of 462 diproline segments in protein crystal structures reveals 25 examples of the alpha(R)-alpha(R) conformation followed by a helix. Modeling and energy minimization studies suggest that both P-II-alpha(R) and alpha(R)-alpha(R) conformations have very similar energies in the model hexapeptide 1

Texts "Con and Pro" : The Early Modern Medical Controversy over Tobacco

The habit of "drinking smoke" , meaning tobacco smoking, caused a true controversy in early modern England. The new substance was used both for its alleged therapeutic properties as well as its narcotic effects. The dispute over tobacco continues the line of written controversies which were an important means of communication in the sixteenth and seventeenth century Europe. The tobacco controversy is special among medical controversies because the recreational use of tobacco soon spread and outweighed its medicinal use, ultimately causing a social and cultural crisis in England. This study examines how language is used in polemic discourse and argumentation. The material consists of medical texts arguing for and against tobacco in early modern England. The texts were compiled into an electronic corpus of tobacco texts (1577 1670) representing different genres and styles of writing. With the help of the corpus, the tobacco controversy is described and analyzed in the context of early modern medicine. A variety of methods suitable for the study of conflict discourse were used to assess internal and external text variation. The linguistic features examined include personal pronouns, intertextuality, structural components, and statistically derived keywords. A common thread in the work is persuasive language use manifested, for example, in the form of emotive adjectives and the generic use of pronouns; the latter is especially pronounced in the dichotomy between us and them. Controversies have not been studied in this manner before but the methods applied have supplemented each other and proven their suitability in the study of conflictive discourse. These methods can also be applied to present-day materials.