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This combined experimental and theoretical study answers the question whether the intramolecular hydrogen-bond strength in amino alcohols is dependent on the ring size. For this purpose, the rotational spectrum of the 3-aminopropanol-H2O van der Waals complex was recorded using Fourier-transform microwave spectroscopy and fit to the rotational, quadrupole coupling, and centrifugal distortion constants of the Watson A-reduction Hamiltonian. The experimental results are consistent with an ab initio conformation calculated at the MP2/6-311++G(d,p) level that involves the lowest energy 3-aminopropanol monomer and consists of a hydrogen bonding network. The calculated global minimum ab initio complex however comprises a higher energy monomer conformation of 3-aminopropanol. Upon complex formation with water, the O-H····N intramolecular hydrogen bond and OCCN backbone conformation of the lower energy monomer remain unchanged, in contrast to 2-aminoethanol. This behavior is consistent with the increasing strength of the intramolecular hydrogen bond of linear amino alcohols as a function of increasing chain length. [ABSTRACT FROM AUTHOR]

Vascularendothelial growth factor (VEGF) activity is highly regulatedvia sequestering within the ECM and cell-demanded proteolysis to releasethe sequestered VEGF. Numerous studies have demonstrated that VEGFactivity mediates cellular events leading to angiogenesis and capillaryformation in vivo. This has motivated the study of biomaterials tosustain VEGF release, and in many cases, the materials are inspiredby the structure and function of the native ECM. However, there remainsa need for materials that can bind to VEGF with high specificity,as the in vivo environment is rich in a variety of growth factors(GFs) and GF-binding moieties. Here we describe a strategy to controlVEGF release using hydrogel microspheres with tethered peptides derivedfrom VEGF receptor 2 (VEGFR2). Using biomaterials covalently modifiedwith varying concentrations of two distinct VEGFR2-derived peptideswith varying serum stability, we analyzed both biomaterial and environmentalvariables that influence VEGF release and activity. The presence oftethered VEGF-binding peptides (VBPs) resulted in significantly extendedVEGF release relative to control conditions, and the resulting releasedVEGF significantly increased the expansion of human umbilical veinendothelial cells in culture. VEGF release rates were also stronglyinfluenced by the concentration of serum. The presence of Feline McDonoughSarcoma-like tyrosine kinase 1 (sFlt-1), a serum-borne receptor fragmentderived from VEGF receptor 1, increased VEGF release rates, althoughsFlt-1 was not sufficient to recapitulate the release profile of VEGFin serum. Further, the influence of serum on VEGF release was notdue to protease activity or nonspecific VEGF interactions in the presenceof serum-borne heparin. VEGF release kinetics correlated well witha generalizable mathematical model describing affinity-mediated releaseof VEGF from hydrogel microspheres in defined conditions. Modelingresults suggest a potential mechanism whereby competition betweenVEGF and multiple VEGF-binding serum proteins including sFlt-1, solublekinase insert domain receptor (sKDR), and α2-macroglobulin (α2-M)likely influenced VEGF release from microspheres. The materials andmathematical model described in this approach may be useful in a rangeof applications in which sustained, biologically active GF releaseof a specific GF is desirable. [ABSTRACT FROM AUTHOR]

Understanding the processes by which stem cells give rise to de novo tissues is an active focus of stem cell biology and bioengineering disciplines. Instructive morphogenic cues surrounding the stem cell during morphogenesis create what is referred to as the stem cell microenvironment. An emerging paradigm in stem cell bioengineering involves "biologically driven assembly," in which stem cells are encouraged to largely define their own morphogenesis processes. However, even in the case of biologically driven assembly, stem cells do not act alone. The properties of the surrounding microenvironment can be critical regulators of cell fate. Stem cell-material interactions are among the most well-characterized microenvironmental effectors of stem cell fate and establish a signaling "context" that can define the mode of influence for morphogenic cues. Here we describe illustrative examples of cell-material interactions that occur during in vitro stem cell studies, with an emphasis on how cell-material interactions create instructive contexts for stem cell differentiation and morphogenesis.