Adoptive immunotherapy of murine cytomegalovirus adrenalitis in the immunocompromised host: CD4-helper-independent antiviral function of CD8-positive memory T lymphocytes derived from latently infected donors.

The ability of memory T lymphocytes derived from latently infected mice to control murine cytomegalovirus disease in the immunocompromised host was studied by adoptive transfer experiments. At a stage of pathogenesis when virus had already colonized target tissues, a therapeutic antiviral function could be ascribed to the CD8+ subset. This in vivo function was not restricted to sites in which intravenously infused lymphocytes usually are trapped or home in, such as the lungs or the spleen, respectively, but was also evident in the adrenal glands, a site to which antiviral effector cells have to specifically migrate. Specific infiltration of adrenal gland cortical tissue by donor-derived CD8+ memory T lymphocytes was demonstrated. CD4+ memory T lymphocytes had no antiviral effect by themselves and also were not required for the function of the CD8+ effector cells in this short-term immunotherapy model. These findings should help settle the debate about which subset of T lymphocytes comprises the effector cells that can directly control cytomegalovirus infection in the murine model system.     

1H-nmr studies of polyoxyethylene-bound homo-oligo-L-methionines

The use of ¹H-nmr spectroscopy is demonstrated to be a useful analytical method to characterize the structure of synthetic peptides attached to soluble, macromolecular polyoxyethylene (POE) supports in the liquid-phase method (LPM) of peptide synthesis. We report an extensive 360-MHz ¹H-nmr study of POE-bound homo-oligo-L -methionine peptides. A combination of high field and selective saturation or Redfield pulse methods allows resolution of individual backbone NH and α-CH resonances of dilute peptides in the presence of strong resonances from macromolecular POE and/or protonated solvents. The nmr spectra for the POE-bound peptides in CDCl₃ are qualitatively similar to those of the low-molecular-weight Boc-L -Met_n-OMe peptide esters. This corroborates other observations that POE has little effect on peptide stucture. The backbone α-CH region of peptides is overlapped by signals from the terminal oxyethylene group of POE, but the peptide side-chain and low-field backbone NH resonances are well resolved. In trifluoroethanol the Boc-(L -Met)_n-NH-POE heptamer and octamer adopt the right-handed α-helical structure, and the present nmr studies provide evidence for two strong intramolecular hydrogen bonds to stabilize the helices. In water, the N-deblocked derivatives, (L -Met)_n-NH-POE oligomers adopt β-sheet structure and manifest well-resolved nonequivalent NH resonances with 6–7 Hz ³J_NH-CH coupling constants.     

Molecular dynamics conformational search of six cyclic peptides used in the template assembled synthetic protein approach for protein de novo design.

Six cyclic peptides, designed to act as topological templates in the TASP (template assembled synthetic protein) approach in protein de novo design, were investigated employing a 100-ps, 900-K molecular dynamics conformational search. The peptides are composed of two Lys-X-Lys (X = Gly, Ala) tripeptides connected at its N- and C-terminal end by a Pro-Gly motif and a cystine bridge (I), two Pro-Gly units (II), naphthalene derivatives (III), and tetrahydronaphthalene derivatives of different stereochemistry (IV-VI). The molecular dynamics conformational search established that template I had beta-sheet like geometry. Templates II-VI showed different preferential geometries, among them, e.g., distinct preferences for type V turns in Pro-Gly containing peptides and close spatial arrangement of hydrophobic naphthalene moieties. The orientation of the lysine side chains within preferential geometries of the individual templates is analyzed and a tentative evaluation for their potential to stabilize TASP molecules of 4-helix bundle topology is given.     

Conformation studies on oligoalanines, substance P, and the myoglobin sequence (66-73). Circular dichroism of polyethyleneglycol-bound peptides]

The conformation of polyethylene glycol-bound peptides, synthesized by the liquid-phase method, was investigated. This marcromolecular C-terminal protecting group is transparent in the visible and the ultraviolet range to 190 nm and solubilizes peptides in many different solvents. The CD spectra of the polymer-bound myoglobin sequence 66–73 and of the biologically active undecapeptide “substance P” were measured in each step of the synthesis. In both examples the formation of a secondary structure during the growth of the peptide chain was found. In the hydrophobic octapeptide containing the myoglobin sequence 66–73, the influence of either the blocked or the free N-terminal amino group on the conformation was observed. The blocked octapeptide in trifluoroethanol showed a higher degree of α-helix contribution than in its free state. The conformation of the polyethylene glycol-bound nona- and decaalanine in trifluoroethanol and water was determined. The peptide with a free amino end group has β-conformation in trifluoroethanol as well as in water. The corresponding N-Boc-protected derivatives show helical structure. The amino end group has a decisive influence on the formation of β-structure. The method of CD investigation of polymer-bound peptide sequences during the peptide synthesis in solution enables one to determine the influence of protecting groups and the chain end of a peptide on its conformation. It is also possible to study the relationship between the secondary structure, the chain length, and the kinetic of the coupling reaction in different solvents. Since the crystallization method for the liquid-phase peptide synthesis allows one to synthesize peptides in very short time, a new method of studying peptide conformations is opened.     

Molecular dynamics simulation on the effect of transition metal binding to the N-terminal fragment of amyloid-β

Abstract

We report molecular dynamics simulations of three possible adducts of Fe(II) to the N-terminal 1–16 fragments of the amyloid-β peptide, along with analogous simulations of Cu(II) and Zn(II) adducts. We find that multiple simulations from different starting points reach pseudo-equilibration within 100–300?ns, leading to over 900?ns of equilibrated trajectory data for each system. The specifics of the coordination modes for Fe(II) have only a weak effect on peptide secondary and tertiary structures, and we therefore compare one of these with analogous models of Cu(II) and Zn(II) complexes. All share broadly similar structural features, with mixture of coil, turn and bend in the N-terminal region and helical structure for residues 11–16. Within this overall pattern, subtle effects due to changes in metal are evident: Fe(II) complexes are more compact and are more likely to occupy bridge and ribbon regions of Ramachandran maps, while Cu(II) coordination leads to greater occupancy of the poly-proline region. Analysis of representative clusters in terms of molecular mechanics energy and atoms-in-molecules properties indicates similarity of four-coordinate Cu and Zn complexes, compared to five-coordinate Fe complex that exhibits lower stability and weaker metal–ligand bonding.

Communicated by Ramaswamy H. Sarma     

Continuous purification of antibodies from cell culture supernatant with aqueous two-phase systems: From concept to process

An aqueous two-phase extraction (ATPE) process based on a PEG/phosphate system was developed for the capture of human immunoglobulin G and successfully applied to a Chinese hamster ovary and a PER.C6® cell supernatant. A continuous ATPE process incorporating three different steps (extraction, back-extraction, and washing) was set up and validated in a pump mixer-settler battery. Most of the higher molecular weight cell supernatant impurities were removed during the extraction step, while most of the lower molecular weight impurities were removed during the subsequent steps. A global recovery yield of 80% and a final protein purity of more than 99% were obtained for the IgG purification from a CHO cell supernatant, representing a 155-fold reduction in the protein/IgG ratio. For the purification of IgG from a PER.C6® cell supernatant, a global recovery yield of 100%, and a host cell protein purity were attained, representing a 22-fold reduction in the host cell protein/IgG ratio. These results, thus, open promising perspectives for the application of the developed ATPE process as a platform for the capture of antibodies. In fact, this new process has shown the ability to successfully recover and purify different antibodies from distinct cell culture supernatants. This technology can also overcome some of the limitations encountered using the typical chromatographic processes, besides inherent advantages of scalability, process integration, capability of continuous operation, and economic feasibility.     

Versatile synthesis of Boc protected hydrazinoacetic acid and its application to the chemoselective ligation of TASP molecules

This paper describes a convenient synthesis of protected hydrazine derivatives, i.e. 1,2-bis-Boc-hydrazinoacetic acid, and its application for hydrazone ligation techniques in convergent template assembled synthetic protein (TASP) synthesis.