Aqueous reductive amination using a dendritic metal catalyst in a dialysis bag

• Jorgen S. Willemsen,
• Jan C. M. van Hest and
• Floris P. J. T. Rutjes

Beilstein J. Org. Chem. 2013, 9, 960–965, doi:10.3762/bjoc.9.110

• nonmagnetic [13][14] or magnetic ones [15][16], which can be contained in semipermeable membranes and hence be physically separated from other catalysts. Nanoparticles, however, may be unstable, and stabilizers, which may affect the catalyst behavior, are often necessary to prevent aggregation [17][18

Synthesis and evaluation of cell-permeable biotinylated PU-H71 derivatives as tumor Hsp90 probes

• Tony Taldone,
• Anna Rodina,
• Erica M. DaGama Gomes,
• Matthew Riolo,
• Hardik J. Patel,
• Raul Alonso-Sabadell,
• Danuta Zatorska,
• Maulik R. Patel,
• Sarah Kishinevsky and
• Gabriela Chiosis

Beilstein J. Org. Chem. 2013, 9, 544–556, doi:10.3762/bjoc.9.60

• biology. Here, we present a systematic approach to identify biotinylated analogues of the Hsp90 inhibitor PU-H71 that are capable of permeating cell membranes so as to enable the investigation of Hsp90 complexes in live cells. The identified derivative 2g can isolate Hsp90 through affinity purification

• tumor-by-tumor basis [13]. Therefore, we believe that there is considerable value in preparing biotinylated analogues of PU-H71 (1a) with the ability to permeate cell membranes so as to enable the investigation of oncogenic Hsp90 complexes in live cells. In contrast to PU-H71 beads, which are limited to

• purpose of identifying compounds capable of permeating cancer-cell membranes, binding selectively to intracellular oncogenic Hsp90 in live cancer cells, and able to trap and isolate Hsp90 bound to tumor-specific onco-client proteins. Because the biotin tag enables pull-down experiments through subsequent

A peptidic hydrogel that may behave as a “Trojan Horse”

• Nicola Castellucci,
• Giorgio Sartor,
• Natalia Calonghi,
• Carola Parolin,
• Giuseppe Falini and
• Claudia Tomasini

Beilstein J. Org. Chem. 2013, 9, 417–424, doi:10.3762/bjoc.9.44

• this “Trojan Horse” strategy. Many peptides can penetrate mammalian cell membranes and take cargo with them. To enable penetration, initial binding of the peptide to the cell surface through electrostatic interactions with lipids, presumably followed by membrane destabilization to allow translocation

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

Towards a biocompatible artificial lung: Covalent functionalization of poly(4-methylpent-1-ene) (TPX) with cRGD pentapeptide

• Lena Möller,
• Christian Hess,
• Jiří Paleček,
• Yi Su,
• Axel Haverich,
• Andreas Kirschning and
• Gerald Dräger

Beilstein J. Org. Chem. 2013, 9, 270–277, doi:10.3762/bjoc.9.33

• are based on polymeric hollow-fiber membranes that serve as an interface between blood and gas streams (Figure 1). The material must allow adequate gas exchange thus providing CO2 removal and O2 delivery for patients with respiratory or ventilatory failure. The thermoplastic polymer poly(4-methylpent

• the negative side effects of the artificial surface can be significantly reduced by seeding endothelial cells (ECs) onto a heparin/albumin-coated TPX surface [5]. Although these endothelialized membranes showed improved hemocompatibility, the cells were easily detached from the membrane due to the

• water-soluble protein coating, which is necessary for the cell attachment. In this paper, we disclose a strategy to strongly attach ECs to TPX 2 membranes by covalent functionalization of the chemically rather inert material with a cyclic peptide, containing the RGD (arginine-glycine-asparagine) amino

Hydrophobic analogues of rhodamine B and rhodamine 101: potent fluorescent probes of mitochondria in living C. elegans

• Laurie F. Mottram,
• Safiyyah Forbes,
• Brian D. Ackley and
• Blake R. Peterson

Beilstein J. Org. Chem. 2012, 8, 2156–2165, doi:10.3762/bjoc.8.243

• synthesized that replace a carboxylate with a methyl group or other less polar functionality. These hydrophobic analogues are generally more effective at penetrating cellular membranes [2][4]. Rhodamines such as rhodamine 123 (4), rhodamine B (5), basic violet 11 (6), rhodamine 6G (7), and rhodamine 101 (8

• mitochondrial inner membranes (typically −120 to −180 mV, depending on cell type) [6][7][8][9]. This membrane potential is critical for ATP synthesis, and is generated by pumping of protons across the mitochondrial inner membrane by the respiratory chain. Many delocalized lipophilic cations preferentially

• lower concentrations than the more polar rhodamine 123 (4), rhodamine B (5), rhodamine 6G (7), and rhodamine 101 (8) fluorophores. Although basic violet 11 (6) was relatively potent, this compound appeared to be of low selectivity, staining multiple intracellular structures including membranes

Multivalent display of the antimicrobial peptides BP100 and BP143

• Imma Güell,
• Rafael Ferre,
• Kasper K. Sørensen,
• Esther Badosa,
• Iteng Ng-Choi,
• Emilio Montesinos,
• Eduard Bardají,
• Lidia Feliu,
• Knud J. Jensen and
• Marta Planas

Beilstein J. Org. Chem. 2012, 8, 2106–2117, doi:10.3762/bjoc.8.237

• , these peptides share several characteristics: the sequence length is typically between 12 to 59 amino acids, they bear a positive charge of +2 to +9, and they show an amphipathic character. The electrostatic interaction of antimicrobial peptides with membranes is a key factor in determining their

• occasionally been reported that an improved binding to microbial membranes and thus an improved antimicrobial activity can be achieved if several copies of an antimicrobial peptide are linked together to form multimeric species [9][10][11][12][13][14][15]. The hypothesis of the assembly model is based on

• . Monomeric undecapeptide BP100 also became moderately structured in 50% TFE with an α-helical content of 21%. Discussion Several studies have demonstrated that covalently tethering a number of peptides to a template can improve overall avidity for targets such as cell membranes [9][10][11][12][13][14][15

The multicomponent approach to N-methyl peptides: total synthesis of antibacterial (–)-viridic acid and analogues

• Ricardo A. W. Neves Filho,
• Sebastian Stark,
• Bernhard Westermann and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2012, 8, 2085–2090, doi:10.3762/bjoc.8.234

• . This fact suggests that 1 does not act just by engaging bacterial membranes as most antibacterial peptides do [49], but that it may bind to a specific target. Conclusion These results highlight the usefulness of the Ugi-4CR for the diversity-oriented synthesis of natural N-methyl peptides, such as

Chemical modification allows phallotoxins and amatoxins to be used as tools in cell biology

• Jan Anderl,
• Hartmut Echner and
• Heinz Faulstich

Beilstein J. Org. Chem. 2012, 8, 2072–2084, doi:10.3762/bjoc.8.233

• been shown that nona-arginine is many times more efficient than Tat-peptide, suggesting that the internalization effect of Tat-peptide is mainly due to its eight cationic side chains [30]. Attachment to plasma membrane determines the rate of internalization Plasma membranes of cells in culture

• native phalloidin, set free in all cases. Attachment to the plasma membrane can also occur by electrostatic forces and, thus, may be behind the internalization effect observed with polylysine or oligoarginine as well. Plasma membranes expose numerous negatively charged components that can attract oligo

Dimerization of a cell-penetrating peptide leads to enhanced cellular uptake and drug delivery

• Jan Hoyer,
• Ulrich Schatzschneider,
• Michaela Schulz-Siegmund and
• Ines Neundorf

Beilstein J. Org. Chem. 2012, 8, 1788–1797, doi:10.3762/bjoc.8.204

• TAT turned out to have no or little effect on translocation through cellular [14][16] or model [17] membranes. Only a branched trimeric variant of TAT was observed to have a major impact on the internalization behavior [14]. In order to gain insight into the mechanism of cell entry of (sC18)2, we

• also plausible for PAD, since it was shown to interact with mitochondrial membranes; however, it does not cause cell death unless it is internalized into the cytosol [27]. The failure of the cytostatic compounds to induce cytotoxicity is due to their limited capability to cross the cellular membrane

Modulating the activity of short arginine-tryptophan containing antibacterial peptides with N-terminal metallocenoyl groups

• H. Bauke Albada,
• Alina-Iulia Chiriac,
• Michaela Wenzel,
• Maya Penkova,
• Julia E. Bandow,
• Hans-Georg Sahl and
• Nils Metzler-Nolte

Beilstein J. Org. Chem. 2012, 8, 1753–1764, doi:10.3762/bjoc.8.200

• bulk (tR = 17.2 min) whereas the second peptide has only two positive charges and four units of lipophilic bulk (tR = 20.1 min). Whereas it is known that tryptophan residues function as membrane anchors [42], details of the interaction between metallocene derivatives and bacterial membranes are far

• the bacterial strains. Since the biological world is chiral, it is not surprising to see some small differences between both chiral forms of the synAMPs. Similar differences in the interaction with chiral molecules and biological membranes have been described before [46][47][48], although only in a

• , ruthenocene and its derivatives typically undergo irreversible two-electron redox chemistry. Whether this difference in redox chemistry of the two metallocenes could interplay with the piezoelectric properties of phospholipid membranes [63] remains to be determined. Ruthenocene is known to have more extended

Mannose-decorated cyclodextrin vesicles: The interplay of multivalency and surface density in lectin–carbohydrate recognition

• Ulrike Kauscher and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2012, 8, 1543–1551, doi:10.3762/bjoc.8.175

• Ulrike Kauscher Bart Jan Ravoo Organic Chemistry Institute, Westfälische Wilhelms-Universität Münster, Correnstraße 40, 48149 Münster, Germany 10.3762/bjoc.8.175 Abstract Cyclodextrin vesicles are versatile models for biological cell membranes since they provide a bilayer membrane that can easily

• development of drug-delivery systems [3]. Synthetic bilayer vesicles are a versatile model for biological cell membranes, and there are a substantial number of reports on synthetic glycolipids that mimic the glycocalyx [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Multivalent

• guest interaction with the surface of the vesicles has become a useful system to investigate recognition, adhesion and fusion of biological cell membranes [24][25][26]. In this context, amphiphilic cyclodextrins are a promising platform due to their ability to form stable bilayer vesicles that can be

Design of a novel tryptophan-rich membrane-active antimicrobial peptide from the membrane-proximal region of the HIV glycoprotein, gp41

• Evan F. Haney,
• Leonard T. Nguyen,
• David J. Schibli and
• Hans J. Vogel

Beilstein J. Org. Chem. 2012, 8, 1172–1184, doi:10.3762/bjoc.8.130

• sequence as gp41w-KA except that all of the Trp residues, apart from Trp8, have been replaced by Phe residues. Because the Trp and Phe amino-acid side chains insert in a different manner into membranes, it is interesting to examine the effect of replacing the interface-binding indole groups [13] with the

• suspensions and the resulting lipid and peptide mixtures were examined by differential scanning calorimetry (DSC) to determine the effect of the peptides on the thermotropic phase behaviour of phospholipids. Eukaryotic membranes typically have a high phosphatidylcholine content, while bacterial membranes are

• preference for the interfacial region of biological membranes [8][9], while the cationic residues are responsible for the initial electrostatic attraction to the negatively charged bacterial cell [7][22]. In this work, the membrane proximal region of gp41 was chosen as a starting point from which to design a

Partial thioamide scan on the lipopeptaibiotic trichogin GA IV. Effects on folding and bioactivity

• Marta De Zotti,
• Barbara Biondi,
• Cristina Peggion,
• Matteo De Poli,
• Haleh Fathi,
• Simona Oancea,
• Claudio Toniolo and
• Fernando Formaggio

Beilstein J. Org. Chem. 2012, 8, 1161–1171, doi:10.3762/bjoc.8.129

• (CD), FT-IR absorption, and NMR. Finally, we carried out fluorescence leakage experiments in model membranes and antibacterial assays on a large set of both Gram-positive and Gram-negative strains. Results and Discussion Peptide synthesis The total syntheses of the three monothionated ψ[CS-NH

• analogues maintain the mixed 310-/α-helical structure and the self-association propensity of the native lipopeptide. They also preserve, at least to a great extent, its well-established capability to interact with model phospholipid membranes and to exhibit activity against Gram-positive bacterial strains

Similarity analysis, synthesis, and bioassay of antibacterial cyclic peptidomimetics

• Workalemahu M. Berhanu,
• Mohamed A. Ibrahim,
• Girinath G. Pillai,
• Alexander A. Oliferenko,
• Levan Khelashvili,
• Farukh Jabeen,
• Bushra Mirza,
• Farzana Latif Ansari,
• Ihsan ul-Haq,
• Said A. El-Feky and
• Alan R. Katritzky

Beilstein J. Org. Chem. 2012, 8, 1146–1160, doi:10.3762/bjoc.8.128

• product purification [25][26][27][28][29]. According to the literature [30][31], most antimicrobial cyclic peptides are active in their cationic form. Cationic peptides are considered advantageous, because they adhere better to the outer anionic parts of phospholipid membranes. Although anionic peptides

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• type [87]. The trans→cis photoisomerization of 4,4'-trimethylammonium methyl substituted azobenzene produced an increase in the concentration of acetylcholine agonists as a result of the specific interaction of both isomers with the acetylcholine receptor that is present in excitable membranes. In this

• way, it is possible to control the permeability changes, allowing the ion motion during the generation of the bioelectric impulse. The isomerization of azocompounds has been used as a synthetic tool to control the opening and closing of pores in cellular membranes, essential for the transport of ions

An easily accessible sulfated saccharide mimetic inhibits in vitro human tumor cell adhesion and angiogenesis of vascular endothelial cells

• Grazia Marano,
• Claas Gronewold,
• Martin Frank,
• Anette Merling,
• Christian Kliem,
• Sandra Sauer,
• Manfred Wiessler,
• Eva Frei and
• Reinhard Schwartz-Albiez

Beilstein J. Org. Chem. 2012, 8, 787–803, doi:10.3762/bjoc.8.89

• with increasing concentrations of GSF is shown in Figure 1. GSF had a cytostatic effect at 2.5 mM beyond 24 h and exhibited cytotoxic effects after 48 h at 5 mM. We also performed cytotoxicity assays by counting cells after trypan-blue staining for disrupted membranes, but the standard deviations are

Synthesis and characterization of a novel carboxyl group containing (co)polyimide with sulfur in the polymer backbone

• Miroslav Mrsevic,
• David Düsselberg and
• Claudia Staudt

Beilstein J. Org. Chem. 2012, 8, 776–786, doi:10.3762/bjoc.8.88

• air leading to a change in optical properties, which often causes undesired optical aberrations [9]. It has been shown that cross-linking can significantly inhibit swelling phenomena in membranes prepared from DABA (3,5-diaminobenzoic acid) functionalized (co)polyimides [10][11][12]. This approach is

Triterpenoid saponins from the roots of Acanthophyllum gypsophiloides Regel

• Elena A. Khatuntseva,
• Vladimir M. Men’shov,
• Alexander S. Shashkov,
• Yury E. Tsvetkov,
• Rodion N. Stepanenko,
• Raymonda Ya. Vlasenko,
• Elvira E. Shults,
• Genrikh A. Tolstikov,
• Tatjana G. Tolstikova,
• Dimitri S. Baev,
• Vasiliy A. Kaledin,
• Nelli A. Popova,
• Valeriy P. Nikolin,
• Pavel P. Laktionov,
• Anna V. Cherepanova,
• Tatiana V. Kulakovskaya,
• Ekaterina V. Kulakovskaya and
• Nikolay E. Nifantiev

Beilstein J. Org. Chem. 2012, 8, 763–775, doi:10.3762/bjoc.8.87

• whether traces or decomposition products of ingested saponins enter the blood stream through the permeable membranes of mucosal cells. For compounds 1, 2 and saponin from Quillaja bark (Sigma) as a reference compound, the study on in vitro hemolysis was carried out. The obtained data confirmed high

Synthesis and antifungal properties of papulacandin derivatives

• Marjolein van der Kaaden,
• Eefjan Breukink and
• Roland J. Pieters

Beilstein J. Org. Chem. 2012, 8, 732–737, doi:10.3762/bjoc.8.82

• Marjolein van der Kaaden Eefjan Breukink Roland J. Pieters Department of Medicinal Chemistry and Chemical Biology. Utrecht Institute for Pharmaceutical Sciences, Utrecht University, P.O. Box 80082, 3508 TB Utrecht, The Netherlands Department of Biochemistry of Membranes, Bijvoet Centre for

Investigation of the network of preferred interactions in an artificial coiled-coil association using the peptide array technique

• Raheleh Rezaei Araghi,
• Carsten C. Mahrenholz,
• Rudolf Volkmer and
• Beate Koksch

Beilstein J. Org. Chem. 2012, 8, 640–649, doi:10.3762/bjoc.8.71

• protocols by using a SPOT synthesizer (Intavis, Köln, Germany) as described in detail in [15]. The peptides were synthesized on amino-functionalized cellulose membranes (Whatman, Maidstone, Great Britain) of the ester type prepared by modifying cellulose paper with Fmoc-β-alanine as the first spacer residue

• assembled on these membranes by using 0.3 M solutions of Fmoc-amino acid-OPfp in 1-methyl-2-pyrrolidone (NMP). The side-chain protection of the Fmoc-amino acids used was as follows: Glu, Asp (Ot-Bu); Ser, Thr, Tyr (t-Bu); His, Lys, Trp (Boc); Asn, Gln, Cys (Trt); Arg (Pbf). After the last coupling step, the

• -cyanocinnamic acid was used as a matrix for MALDI–TOF (Applied Biosystems, Forster City, USA) MS analysis. Binding studies on cellulose membranes [26]: All incubation and washing steps were carried out under gentle shaking and at room temperature. After washing of the membrane with ethanol once for 10 min and

An easy α-glycosylation methodology for the synthesis and stereochemistry of mycoplasma α-glycolipid antigens

• Yoshihiro Nishida,
• Yuko Shingu,
• Yuan Mengfei,
• Kazuo Fukuda,
• Hirofumi Dohi,
• Sachie Matsuda and
• Kazuhiro Matsuda

Beilstein J. Org. Chem. 2012, 8, 629–639, doi:10.3762/bjoc.8.70

• (10:1), it may be possible to assume that the mycoplasma GGPLs and the related 3-O-(α-D-glycopyranosyl)-sn-glycerolipids can constitute cytoplasm membranes in good cooperation with ubiquitous phospholipids without inducing stereochemical stress at the membrane. The GGPL-I isomer I-b showed an overall

• also in physicochemical contact with other chiral constituents in cell membranes [44][45]. Experimental General methods Infrared (IR) spectra were recorded on a JASCO FT/IR-230 Fourier transform infrared spectrometer on KBr disks. All 1H NMR (500 MHz) spectra were recorded by using a Varian INOVA-500

Cyanoethylation of the glucans dextran and pullulan: Substitution pattern and formation of nanostructures and entrapment of magnetic nanoparticles

• Kathrin Fiege,
• Heinrich Lünsdorf,
• Sevil Atarijabarzadeh and
• Petra Mischnick

Beilstein J. Org. Chem. 2012, 8, 551–566, doi:10.3762/bjoc.8.63

• purchased from Fluka. Acrylonitrile (AN) was supplied from Janssen. DMSO [puriss, absolute, over molecular sieves (H2O ≤ 0.01%), ≥ 99.5% (GC)] was obtained from Sigma-Aldrich. Deionized water was used. Dialysis was performed with molecular porous dialysis membranes (molecular weight cut off 3.5 kDa) from

Synthesis and biological evaluation of nojirimycin- and pyrrolidine-based trehalase inhibitors

• Davide Bini,
• Francesca Cardona,
• Matilde Forcella,
• Camilla Parmeggiani,
• Paolo Parenti,
• Francesco Nicotra and
• Laura Cipolla

Beilstein J. Org. Chem. 2012, 8, 514–521, doi:10.3762/bjoc.8.58

• 19th century in Aspergillus niger [4] and S. cerevisiae [5], and has since then been reported in several other organisms, including mammals, where it is found both in the kidney brush border membranes [6] and in the intestinal villae membranes [7]. While the role of trehalase in the kidney has not been

Novel fatty acid methyl esters from the actinomycete Micromonospora aurantiaca

• Jeroen S. Dickschat,
• Hilke Bruns and
• Ramona Riclea

Beilstein J. Org. Chem. 2011, 7, 1697–1712, doi:10.3762/bjoc.7.200

• important building blocks of biological systems. They fulfill various physiological functions, such as cell-membrane assembly or, as highly reduced carbon compounds, energy storage, and are therefore found in every single living cell on earth. In bacteria the cell membranes are mainly formed from

• of bacterial cell membranes can be tuned, e.g., by the introduction of methyl branches or olefinic double bonds [1]. The biosynthesis of FAs is a repetitive chain elongation process catalysed in animals and fungi by multifunctional megasynthases, and in plants or bacteria by a set of discrete enzymes