Conformationally Restricted Peptides from Rice Proteins Elicit Antibodies That Recognize the Corresponding Native Protein in ELISA Assays.

The rice hoja blanca virus (RHBV), transmitted by the planthopper insect Tagosodes orizicolus, is a disease that attacks rice and generates significant production losses in Colombia. Fedearroz 2000 and Colombia I commercial rice varieties, which have different resistance levels to the disease, were selected in this study. To identify proteins associated to the insect and virus signaling, a comparative proteomics study was performed. By comparing proteomic profiles, between virus-infected and control group plants in two-dimensional electrophoresis, proteins exhibiting significant changes in abundance were found. In another test, peptide dendrimers containing sequences conformationally restricted to α-helix from four of those rice proteins were synthesized. In the experiment, sera from mice inoculated with peptide dendrimers could recognize the corresponding native protein in ELISA assays. Reported comparative proteomic results provide new insights into the molecular mechanisms of plant response to the RHBV and comprehensive tools for the analysis of new crop varieties. Besides, results from conformational peptide dendrimer approach are promising and show that it is feasible to detect proteins as markers, and may have biological applications by decreasing the susceptibility to proteolytic degradation.

Peptide solubiltty, structure and charge position effect on adsorption by aluminium hydroxide / Efcto de la soluubilidad, la estructura y la posición de cargas de un péptido en la adsorción sobre hidróxido de alumiioo

Solubility, structure and position of charges in a peptide antigen sequence can be mentioned as being amongst the basic features of adsorption. In order to study their effect on adsorption, seven analogue series were synthesized from a MSP-1 peptide sequence by systematically replacing each one of the positions in the peptide sequence by aspartic acid, glutamic acid, serine, alanine, asparagine, glutamine or lysine. Such modifications in analogue peptide sequences showed a non-regular tendency regarding solubility and adsorption data. Aspartic acid and Glutamic acid analogue series showed great improvements in adsorption, especially in peptides where Lysine in position 6 and Arginine in position 13 were replaced. Solubility of position 5 analogue was greater than the position 6 analogue in Aspartic acid series; however, the position 6 analogue showed best adsorption results whilst the Aspartic acid in position 5 analogue showed no adsorption in the same conditions. Nuclear Magnetic Resonance structural analysis revealed differences in the -helical structure extension between these analogues. The Aspartic acid in position 6, located in the polar side of the helix, may allow this analogue to fit better onto the adsorption regions suggesting that the local electrostatic charge is responsible for this behavior.

La solubilidad, la estructura y la posición de las cargas en una secuencia de un péptido antígeno, se encuentran entre las características básicas de la adsorción. Con el fin de estudiar su efecto sobre la adsorción, fueron sintetizadas siete series de análogos de la secuencia de un péptido de la proteína MSP-1, reemplazando sistemáticamente cada una de las posiciones en la secuencia del péptido por ácido aspártico, ácido glutámico, serina, alanina, asparagina, glutamina o lisina. Las modificaciones en las secuencias de los péptidos análogos no mostraron tendencias regulares respecto a los datos de solubilidad y adsorción. Las series de análogos de ácido aspártico y ácido glutámico presentaron grandes incrementos en la adsorción, en especial cuando fueron reemplazadas la lisina de la posición 6 y la arginina de la posición 13. La solubilidad del análogo en posición 5 fue mayor que la del análogo en posición 6 en la serie del ácido aspártico; sin embargo, los mejores resultados en adsorción se obtuvieron al sustituir con ácido aspártico la posición 6, mientras que el análogo con el ácido aspártico en la posición 5 no presentó adsorción a las mismas condiciones. El análisis estructural por resonancia magnética nuclear mostró diferencias en la extensión de la estructura helicoidal entre estos análogos. El ácido aspártico en la posición 6, localizado en la cara polar de la hélice, podría permitir a este análogo ajustarse mejor sobre los sitios de adsorción, sugiriendo que la carga electrostática local es la responsable de este comportamiento.

An alpha helix conformationally restricted peptide is recognized by cervical carcinoma patients' sera.

Human papillomavirus type 16 (HPV-16) represents the major cervical carcinoma associated virus among women, especially in Colombia. It has thus become important to develop reliable inexpensive tests for detecting the presence of this virus. It has been shown that HPV16-E7 oncoprotein structural features have three alpha-helical structures and a loop-like structure. The hydrazone link approach was used to mimic helix secondary substructures. Sera from women with invasive cervical carcinoma were tested against conformationally restricted peptides and their respective linear peptides to identify conformational epitopes. One peptide that was conformationally restricted to an alpha-helix showed very strong positive reaction with sera from women having invasive cervical carcinoma; there was no reaction with sera from patients with other carcinomas, children, or healthy women. NMR studies confirmed this peptide's alpha-helical structure. The observation that constrained protein substructure peptidomimetics can identify new conformationally sensitive antibodies in cervical carcinoma patients' sera is very important, since these antibodies are almost all generated by native proteins, providing a new selection of antibodies for diagnostic and vaccine studies.