3 research outputs found
Deconstructing a Plant Macromolecular Assembly: Chemical Architecture, Molecular Flexibility, And Mechanical Performance of Natural and Engineered Potato Suberins
Periderms
present in plant barks are essential protective barriers
to water diffusion, mechanical breakdown, and pathogenic invasion.
They consist of densely packed layers of dead cells with cell walls
that are embedded with suberin. Understanding the interplay of molecular
structure, dynamics, and biomechanics in these cell wall-associated
insoluble amorphous polymeric assemblies presents substantial investigative
challenges. We report solid-state NMR coordinated with FT-IR and tensile
strength measurements for periderms from native and wound-healing
potatoes and from potatoes with genetically modified suberins. The
analyses include the intact suberin aromatic–aliphatic polymer
and cell-wall polysaccharides, previously reported soluble depolymerized
transmethylation products, and undegraded residues including suberan.
Wound-healing suberized potato cell walls, which are 2 orders of magnitude
more permeable to water than native periderms, display a strikingly
enhanced hydrophilic–hydrophobic balance, a degradation-resistant
aromatic domain, and flexibility suggestive of an altered supramolecular
organization in the periderm. Suppression of ferulate ester formation
in suberin and associated wax remodels the periderm with more flexible
aliphatic chains and abundant aromatic constituents that can resist
transesterification, attenuates cooperative hydroxyfatty acid motions,
and produces a mechanically compromised and highly water-permeable
periderm
Using Solid-State NMR To Monitor the Molecular Consequences of <i>Cryptococcus neoformans</i> Melanization with Different Catecholamine Precursors
Melanins are a class of natural pigments associated with
a wide
range of biological functions, including microbial virulence, energy
transduction, and protection against solar radiation. Because of their
insolubility and structural heterogeneity, solid-state nuclear magnetic
resonance (NMR) spectroscopy provides an unprecedented means to define
the molecular architecture of these enigmatic pigments. The requirement
of obligatory catecholamines for melanization of the pathogenic fungus <i>Cryptococcus neoformans</i> also offers unique opportunities
for investigating melanin development. In the current study, pigments
produced with l-dopa, methyl-l-dopa, epinephrine,
and norepinephrine precursors are compared structurally using <sup>13</sup>C and <sup>1</sup>H magic-angle spinning (MAS) NMR. Striking
structural differences were observed for both aromatic and aliphatic
molecular constituents of the mature fungal pigment assemblies, thus
making it possible to redefine the molecular prerequisites for formation
of the aromatic domains of insoluble indole-based biopolymers, to
rationalize their distinctive physical characteristics, and to delineate
the role of cellular constituents in assembly of the melanized macromolecules
with polysaccharides and fatty acyl chain-containing moieties. By
achieving an augmented understanding of the mechanisms of <i>C. neoformans</i> melanin biosynthesis and cellular assembly,
such studies can guide future drug discovery efforts related to melanin-associated
virulence, resistance to tumor therapy, and production of melanin
mimetics under cell-free conditions
Solid-State <sup>13</sup>C NMR Delineates the Architectural Design of Biopolymers in Native and Genetically Altered Tomato Fruit Cuticles
Plant
cuticles on outer fruit and leaf surfaces are natural macromolecular
composites of waxes and polyesters that ensure mechanical integrity
and mitigate environmental challenges. They also provide renewable
raw materials for cosmetics, packaging, and coatings. To delineate
the structural framework and flexibility underlying the versatile
functions of cutin biopolymers associated with polysaccharide-rich
cell-wall matrices, solid-state NMR spectra and spin relaxation times
were measured in a tomato fruit model system, including different
developmental stages and surface phenotypes. The hydrophilic–hydrophobic
balance of the cutin ensures compatibility with the underlying polysaccharide
cell walls; the hydroxy fatty acid structures of outer epidermal cutin
also support deposition of hydrophobic waxes and aromatic moieties
while promoting the formation of cell-wall cross-links that rigidify
and strengthen the cuticle composite during fruit development. Fruit
cutin-deficient tomato mutants with compromised microbial resistance
exhibit less efficient local and collective biopolymer motions, stiffening
their cuticular surfaces and increasing their susceptibility to fracture