Base-induced side reactions in Fmoc-solid phase peptide synthesis:Minimization by use of piperazine as Nα-deprotectionreagent

Summary Base-induced aspartimide (cyclic imide) and subsequent base adduct formation in the Fmoc-solid phase synthesis of sensitive sequences are serious side reactions that are difficult to both anticipate and control. The effect of extended treatment of piperazine as N^α-Fmoc deprotection reagent on two sensitive peptide sequences was examined. For comparison, other bases were also investigated, including piperidine, 1-hydroxypiperidine, tetrabutylammonium fluoride, and 1,8-diazabicyclo[5.4.0]undec-7-ene. The results showed that all bases induced varying degrees of both aspartimide and, in some cases, base adduct formation, although piperazine caused the least side reaction. Use ofN-(2-hydroxy-4-methoxybenzyl) peptide backbone amide protection was confirmed to confer complete protection against side reaction. In the absence of such protection, for all bases, the use of 1-hydroxybenzotriazole as additive had some, but not complete, beneficial effect in further reducing side reaction. Best results were obtained with piperazine containing 0.1M 1-hydroxybenzotriazole indicating that this reagent merits serious consideration for N^α-deprotection in the Fmoc-solid phase synthesis of base-sensitive sequences. A further advantage of this reagent is that it causes little racemisation of resin-bound C-terminal cysteine, an occasionally serious base-mediated problem in Fmoc-solid phase assembly. A preliminary account of this work was presented at the 25th European Peptide Symposium, Budapest, Hungary, 1998.     

Description of a new Nipergasilus species (Family: Ergasilidae) from the gills of grey mullet

A new Nipergasilus species is described from the gills of the grey mullet Valamugil cunnesius from several localities in India and Pakistan. The new species is closely related to Nipergasilus bora (Yamaguti, 1939) which is also recorded here on three species of grey mullet. The genus Nipergasilus is redefined in order to accommodate the second species.     

Microjet impingement followed by scanning electron microscopy as a qualitative technique to compare cellular adhesion to various biomaterials

Adhesion of cells to biomaterial surfaces is one of the major factors which mediates their biocompatibility. Quantitative or qualitative cell adhesion measurements would be useful for screening new implant materials. Microjet impingement has been evaluated by scanning electron microscopy, to determine to what extent it measures cell adhesion. The shear forces of the impingement, on the materials tested here, are seen to be greater than the cohesive strength of the cells in the impinged area, causing their rupture. The cell bodies are removed during impingement, leaving the sites of adhesion and other cellular material behind. Thus the method is shown not to provide quantification of cell adhesion forces for the metals and culture plastic tested. It is suggested that with highly adherent biomaterials, the distribution and patterns of these adhesion sites could be used for qualitative comparisons for screening of implant surfaces.     

The actin nucleator Spir-1 is a virus restriction factor that promotes innate immune signalling

Cellular proteins often have multiple and diverse functions. This is illustrated with protein Spir-1 that is an actin nucleator, but, as shown here, also functions to enhance innate immune signalling downstream of RNA sensing by RIG-I/MDA-5. In human and mouse cells lacking Spir-1, IRF3 and NF-κB-dependent gene activation is impaired, whereas Spir-1 overexpression enhanced IRF3 activation. Furthermore, the infectious virus titres and sizes of plaques formed by two viruses that are sensed by RIG-I, vaccinia virus (VACV) and Zika virus, are increased in Spir-1 KO cells. These observations demonstrate the biological importance of Spir-1 in the response to virus infection. Like cellular proteins, viral proteins also have multiple and diverse functions. Here, we also show that VACV virulence factor K7 binds directly to Spir-1 and that a diphenylalanine motif of Spir-1 is needed for this interaction and for Spir-1-mediated enhancement of IRF3 activation. Thus, Spir-1 is a new virus restriction factor and is targeted directly by an immunomodulatory viral protein that enhances virus virulence and diminishes the host antiviral responses.     

Linearizing ecological models with time-varying parameters

An ecological model with time-varying parameters can be linearized about a point which is either a local equilibrium or fixed in time, but not in general both. Each choice has its advantages, but neither choice is anywhere near as useful as the linearization of a model with constant parameters. Linearizations of a model of annual plankton cycles can capture some qualitative behavior of the original nonlinear model.     

Lack of response to all-trans retinoic acid supplementation in adult dogs following left pneumonectomy.

We showed previously that removing 55-58% of the lung by right pneumonectomy (R-PNX) in adult dogs triggers compensatory growth of the remaining lung, but removing 42-45% of the lung by left PNX (L-PNX) does not. We also showed that, following R-PNX, supplemental all-trans retinoic acid (RA) selectively enhances alveolar capillary endothelial cell volume (Yan X, Bellotto DJ, Foster DJ, Johnson RL, Jr., Hagler HH, Estrera AS, and Hsia CC. J Appl Physiol 96: 1080-1089, 2004). We hypothesized that RA supplementation might enhance compensation following L-PNX and tested this hypothesis by administering RA (2 mg.kg(-1).day(-1), 4 days/wk) or placebo orally to litter-matched adult foxhounds for 4 mo following L-PNX. Resting lung function was measured under anesthesia. Air and tissue volumes of the remaining lung were assessed by high-resolution computed tomography scan and by detailed postmortem morphometric analysis of the fixed lung. There was no significant difference in resting lung function, lung volume, alveolar structure, or septal ultrastructure between RA and placebo treatment groups. We conclude that RA supplementation does not induce post-PNX compensatory lung growth in the absence of existing cellular growth activities initiated by other primary signals.