Approaches in biotechnological applications of natural polymers

Natural polymers, such as gums and mucilage, are biocompatible, cheap, easily available and non-toxic materials of native origin. These polymers are increasingly preferred over synthetic materials for industrial applications due to their intrinsic properties, as well as they are considered alternative sources of raw materials since they present characteristics of sustainability, biodegradability and biosafety. As definition, gums and mucilages are polysaccharides or complex carbohydrates consisting of one or more monosaccharides or their derivatives linked in bewildering variety of linkages and structures. Natural gums are considered polysaccharides naturally occurring in varieties of plant seeds and exudates, tree or shrub exudates, seaweed extracts, fungi, bacteria, and animal sources. Water-soluble gums, also known as hydrocolloids, are considered exudates and are pathological products; therefore, they do not form a part of cell wall. On the other hand, mucilages are part of cell and physiological products. It is important to highlight that gums represent the largest amounts of polymer materials derived from plants. Gums have enormously large and broad applications in both food and non-food industries, being commonly used as thickening, binding, emulsifying, suspending, stabilizing agents and matrices for drug release in pharmaceutical and cosmetic industries. In the food industry, their gelling properties and the ability to mold edible films and coatings are extensively studied. The use of gums depends on the intrinsic properties that they provide, often at costs below those of synthetic polymers. For upgrading the value of gums, they are being processed into various forms, including the most recent nanomaterials, for various biotechnological applications. Thus, the main natural polymers including galactomannans, cellulose, chitin, agar, carrageenan, alginate, cashew gum, pectin and starch, in addition to the current researches about them are reviewed in this article.. }To the Conselho Nacional de Desenvolvimento Cientfíico e Tecnológico (CNPq) for fellowships (LCBBC and MGCC) and the Coordenação de Aperfeiçoamento de Pessoal de Nvíel Superior (CAPES) (PBSA). This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, the Project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462) and COMPETE 2020 (POCI-01-0145-FEDER-006684) (JAT)

Review Article - Techniques in the treatment of craniovertebral instability

The techniques of craniovertebral region stabilization introduced and used by the senior author over the last 20 years are summarized. The lateral masses of atlas and axis are strong and largely cancellous in nature and can be used for direct implantation of screws. Opening up of the joint and placement of bone graft within the joint stabilizes the region and provides a large area for bone fusion. Distraction of the facets provides an opportunity to treat a range of congenital craniovertebral anomalies. The technique of exposure of the lateral mass of the atlas and axis and the atlantoaxial joint is technically relatively complex and needs precise understanding of anatomy of the vertebral artery and training with cadavers

Nucleophilic Capture of Unsymmetrical Oxyallyl Cations with Indoles under Mild Bronsted Acid Catalysis

© Georg Thieme Verlag Stuttgart. We recently reported a new synthetic method in our laboratory concerning the control of regioselectivity in the addition of nucleophiles, such as indoles, to unsymmetrical oxyallyl cations. These reactive intermediates were readily generated upon ionization of the corresponding α-hydroxy enol ether precursors under catalytic, mild Bronsted acid. Results from our expansive scope of substrate studies revealed that regioselectivity in this reaction could be regulated upon protection of the oxygen atom in the oxyallyl cation moiety as well as modulation of the stereoelectronic effects in the participating α vs. α′ substituents

Free-Radical Carbocyanation of Cyclopropenes: Stereocontrolled Access to All-Carbon Quaternary Stereocenters in Acyclic Systems

Free-radical carbocyanation of cyclopropenes offers straightforward access to tetrasubstituted cyclopropanes in satisfying yields with moderate diastereoselectivity. The incorporation of various functional groups on the cyclopropane ring allows a subsequent base-mediated ring-opening reaction leading to functionalized acyclic systems having an all-carbon quaternary stereocenter

Fiber dissection of the visual pathways: Analysis of the relationship of optic radiations to lateral ventricle: A cadaveric study

Objective: Using a fiber-dissection technique, our aim is to study the fiber bundles of the optic radiation. We focused on the course, the length, anatomical relations with lateral ventricle and the relevance of these finding during surgery in the region. Materials and Methods: Five previously frozen and formalin-fixed cadaveric human brains were used. The dissection was done using the operating microscope. Fiber dissection techniques described by Klingler were adopted. The primary dissection tools were handmade, thin, and wooden and curved metallic spatulas with tips of various sizes. Lateral and inferior temporal approaches were made and the optic fiber tracts were dissected. Results: Resections that extend through the roof of the temporal horn more than 30 mm behind the temporal pole cross the Meyer′s loop. In the middle temporal gyrus approach, resection that is taken through the lateral wall of the temporal horn more than 55-60 mm behind the temporal pole may cross the optic radiation during their course here on the lateral wall. Conclusion: The presented fiber dissection study clarifies the relationship of optic radiation. Such fiber dissection studies are only few in the literature