José Guadalupe Rutiaga-Quiñones

Molecular docking insights into the inhibition of laccase activity by medicarpin

Molecular docking calculations were performed to understand the inhibition mechanism of medicarpin on the lignin degradation enzyme laccase. The study was carried out in two stages. The first stage was performed on a laccase–oligolignol complex, to elucidate the active binding mode in the enzyme that initiates lignin degradation. The second stage was performed on a laccase–medicarpin complex, to understand the inhibitory effect of medicarpin on the enzymatic mechanism. In this two-step procedure, the crystal structure of a laccase (PDB: 1GYC) obtained from Trametes versicolor, a white-rot fungus capable of degrading lignin in wood, was employed because it produces considerable amounts of laccase. The results obtained from the laccase–oligolignol complex indicate that the binding site is located in a pocket that surrounds the T1 copper atom, which is in agreement with experimental reports. The results from the laccase–medicarpin complex indicate that the inhibitory effect occurs by the blockage of a solvent channel in the T. versicolor laccase by a medicarpin conformer, preventing the rapid access of molecular oxygen to the trinuclear T2/T3 copper cluster, and also by the coupling of medicarpin conformers in the T1 site pocket, blocking access by oligolignol molecules. Therefore, this coupling of medicarpin to two sites in laccase interrupts the enzymatic mechanism of lignin degradation. The results of this study may be useful in developing wood-preserving formulations based on medicarpin or similar molecular structures and in expanding the scientific knowledge of laccase activity for biotechnological applications.

Comparison of five pretreatments for the production of fermentable sugars obtained from Pinus pseudostrobus L. wood

To benefit from the use of a waste product such as pine sawdust from a sawmill in Michoacán, Mexico, five different pretreatments for the production of reducing sugars by enzymatic hydrolysis were evaluated (sodium hydroxide, sulfuric acid, steam explosion, organosolv and combined method nitric acid / sodium hydroxide). The main finding of the study was that the pretreatment with 6 % HNO3 and 1 % NaOH led to better yields than those obtained with sodium hydroxide, dilute sulfuric acid, steam explosion, and organosolv pretreatments. Also, HNO3 yields were maximized by the factorial method. With those results the maxima concentration of reducing sugar found was 97.83 ± 1.59, obtained after pretreatment with 7.5 % HNO3 at 120 °C for 30 minutes; followed by 1 % of NaOH at 90 °C for 30 minutes at pH 4.5 for 168 hours with a load enzyme of 25 FPU/g of total carbohydrates. Comparing the results obtained by the authors with those reported in the literature, the combined method was found to be suitable for use in the exploitation of sawdust.

Chemical composition of biomass generated in the guava tree pruning

Psidium guajava L. (Myrtaceae) is a native plant of Central America and is now widely cultivated in many tropical regions of the world for the fruit production. In Mexico, in the guava orchards common practices to control fruit production are: water stress, defoliation and pruning. In this study, we report the chemical composition of the biomass (branches and leaves) generated in the pruning practices. The results ranged as follows: pH (4.98-5.88), soda solubility (39.01-70.49 %), ash (1.87-8.20 %); potassium and calcium were the major inorganic elements in ash. No heavy metals were detected in the studied samples; total solubility (15.21-46.60 %), Runkel lignin (17.77-35.26 %), holocellulose (26.56 -69.49 %), α-cellulose (15.53-35.36 %), hemicelluloses (11.02-34.12 %), tannins in aqueous extracts (3.81-9.06 %), and tannins in ethanolic extracts (3.42-15.24 %).

CONTENIDO DE TANINOS EN LA CORTEZA DE DOS ESPECIES DE PARÁCATA (Erythroxylon compactum Rose y Senna skinneri Benth. Irwin & Barneby)

Forest decline in Desierto de los Leones National Park in Mexico City affects Abies religiosa, a dominant and hard-to-root species in the region. As a result of this decline, the species requires propagation in the region through rooting of cuttings. In this study, a method of vegetative production was developed to determine whether the effect of origin, age of the material, type of hormone used and the presence of decline symptoms affect the rooting capacity of cuttings of this species. Three experiments were conducted, and only the third one produced rooting of cuttings. In this experiment, a substrate composed of peat moss and perlite was used to test rooting of cuttings of two origins, with and without symptoms, generated in two growing seasons and using two auxins (indolbutyric acid and naphthalene acetic acid), keeping the soil moisture between 75-80 %. The combination of these factors produced 16 treatments, which were replicated 50 times. Data were processed by factorial analysis of variance. Results indicate that early December is the best time to collect plant material for rooting of A. religiosa cuttings, as they are the youngest, and that those that received indol-butyric acid rooted the best. Origin and decline symptoms had no effect on rooting. Recibido:14 de junio de 2011 Aceptado: 06 de marzo de 2013 doi: 10.5154/r.rchscfa.2011.06.038 http://www.chapingo.mx/revistas PALABRAS CLAVE: Propagación vegetativa, procedencia, auxinas, edad de estaca, ácido indol-3butírico, ácido naftalenacético.The below-canopy light environment influences the survival, the tree regeneration growth and the development of the understory plant species. Therefore, there has been much interest in measuring the below-canopy light environment. Several instruments, techniques and methods have been developed to measure directly or to estimate indirectly the below-canopy light environment. To date, many comparisons of direct and indirect methods for the measuring and estimation of below-canopy light environment have been conducted in order to determine the best way to measure the light in the understory. In this review a scientific description of the currently instruments, techniques and methods used to measure or to estimate the below-canopy solar radiation is shown. The nature and properties of the different methods, techniques and instruments are commented. Finally, the choice of equipment to meet the needs of the researcher in this topic is supported. Recibido: 29 de febrero de 2012 Aceptado: 12 de febrero de 2013 doi: 10.5154/r.rchscfa.2012.02.014 http://www.chapingo.mx/revistas PALABRAS CLAVE: Radiación solar, luz, medición directa, estimación indirecta, ambiente bajo el dosel arbóreo.The usefulness of forest species in agricultural production systems is an option that helps to reduce the pressure in natural forests; they can also be used in treeless areas. The aim of this study was to evaluate the nutritional quality, germination, development of seedlings grown in nursery and variety of uses of Leucaena lanceolata S. Watson ssp. lanceolata. Edible material and seeds were collected in Tomatlán, Jalisco. Bromatologic analyses, scarification tests and the evaluation of seedlings grown in nursery using three soils with different pH values were performed. The experimental design was completely randomized, with Tukey (P≤0.05) test for media comparison. A survey study, bibliographical revision and review of specimens in the herbariums were used to know the local and potential diversity of uses of this specie. Results show high content of dry matter (97.40 %) and crude protein (29.05 %), greater germination using heat treatments, better seedling development in slightly acid soil (6.57) and the diversity of uses including firewood, forage and timber among others. L. lanceolata represents a viable option to be used in dry tropical silvopastoral systems due to the high nutritional value and the diversity of uses in rural areas. Recibido: 27 de septiembre de 2011 Aceptado: 01 de febrero de 2013 doi: 10.5154/.r.rchscfa.2011.09.070 http://www.chapingo.mx/revistas PALABRAS CLAVE: escarificación, materia seca, proteína cruda, pH,