Sidechain control of porosity closure in multiple peptide-based porous materials by cooperative folding

Porous materials find application in separation, storage and catalysis. We report a crystalline porous solid formed by coordination of metal centres with a glycylserine dipeptide. We prove experimentally that the structure evolves from a solvated porous into a non-porous state as result of ordered displacive and conformational changes of the peptide that suppress the void space in response to environmental pressure. This cooperative closure, which recalls the folding of proteins, retains order in three-dimensions and is driven by the hydroxyl groups acting as H-bond donors in the peptide sequence through the serine residue. This ordered closure is also displayed by multipeptide solid solutions in which the combination of different sequences of amino acids controls their guest response in a non-linear way. This functional control can be compared to the effect of single point mutations in proteins, where the exchange of single amino acids can radically alter structure and functio

Karhunen-Lo\`eve expansion for a generalization of Wiener bridge

We derive a Karhunen-Lo\`eve expansion of the Gauss process $B_t - g(t)\int_0^1 g'(u)\,d B_u$, $t\in[0,1]$, where $(B_t)_{t\in[0,1]}$ is a standard Wiener process and $g:[0,1]\to R$ is a twice continuously differentiable function with $g(0) = 0$ and $\int_0^1 (g'(u))^2\,d u =1$. This process is an important limit process in the theory of goodness-of-fit tests. We formulate two special cases with the function $g(t)=\frac{\sqrt{2}}{\pi}\sin(\pi t)$, $t\in[0,1]$, and $g(t)=t$, $t\in[0,1]$, respectively. The latter one corresponds to the Wiener bridge over $[0,1]$ from $0$ to $0$.Comment: 25 pages, 1 figure. The appendix is extende

Label-free segmentation of co-cultured cells on a nanotopographical gradient

The function and fate of cells is influenced by many different factors, one of which is surface topography of the support culture substrate. Systematic studies of nanotopography and cell response have typically been limited to single cell types and a small set of topographical variations. Here, we show a radical expansion of experimental throughput using automated detection, measurement, and classification of co-cultured cells on a nanopillar array where feature height changes continuously from planar to 250 nm over 9 mm. Individual cells are identified and characterized by more than 200 descriptors, which are used to construct a set of rules for label-free segmentation into individual cell types. Using this approach we can achieve label-free segmentation with 84% confidence across large image data sets and suggest optimized surface parameters for nanostructuring of implant devices such as vascular stents

Strategies to improve spinal cord ischemia in endovascular thoracic aortic repair: Outcomes of a prospective cerebrospinal fluid drainage protocol

PurposeAlthough endovascular repair of thoracic aortic aneurysm has been shown to reduce the morbidity and mortality rates, spinal cord ischemia remains a persistent problem. We evaluated our experience with spinal cord protective measures using a standardized cerebrospinal fluid (CSF) drainage protocol in patients undergoing endovascular thoracic aortic repair.MethodsFrom 2004 to 2006, 121 patients underwent elective (n = 52, 43%) and emergent (n = 69, 57%) endovascular thoracic aortic stent graft placement for thoracic aortic aneurysm (TAA) (n = 94, 78%), symptomatic penetrating ulceration (n = 11, 9%), pseudoaneurysms (n = 5, 4%) and traumatic aortic transactions (n = 11, 9%). In 2005, routine use of a CSF drainage protocol was established to minimize the risks of spinal cord ischemia. The CSF was actively drained to maintain pressures <15 mm Hg and the mean arterial blood pressures were maintained at ≥90 mm Hg. Data was prospectively collected in our vascular registry for elective and emergent endovascular thoracic aortic repair and the patients were divided into 2 groups (+CSF drainage protocol, −CSF drainage protocol). A χ2 statistical analysis was performed and significance was assumed for P < .05.ResultsOf the 121 patients with thoracic stent graft placement, the mean age was 72 years, 62 (51%) were male, and 56 (46%) underwent preoperative placement of a CSF drain, while 65 (54%) did not. Both groups had similar comorbidities of coronary artery disease (24 [43%] vs 27 [41%]), hypertension (44 [79%] vs 50 [77%]), chronic obstructive pulmonary disease (18 [32%] vs 22 [34%]), and chronic renal insufficiency (10 [17%] vs 12 [18%]). None of the patients with CSF drainage developed spinal cord ischemia (SCI), and 5 (8%) of the patients without CSF drainage developed SCI within 24 hours of endovascular repair (P< .05). All patients with clinical symptoms of SCI had CSF drain placement and augmentation of systemic blood pressures to ≥90 mm Hg, and 60% (3 of 5 patients) demonstrated marked clinical improvement.ConclusionPerioperative CSF drainage with augmentation of systemic blood pressures may have a beneficial role in reducing the risk of paraplegia in patients undergoing endovascular thoracic aortic stent graft placement. However, selective CSF drainage may offer the same benefit as mandatory drainage