Drying and Deposition of Picolitre Droplets of Colloidal Suspensions in Binary Solvent Mixtures

Picolitre droplets of colloidal suspensions in a mixture of two solvents are emitted by a drop-on-demand ink jet print head onto coated and uncoated glass substrates. The evaporation rate and internal flows inside the drying droplets are investigated and the deposit pattern formed is related to the drying dynamics. High-speed imaging of the droplet profile from the side al- lows the droplet diameter, height, contact angle and volume to be measured during evaporation. The internal flows throughout dry- ing are visualized by following tracer particles within the fluid with an inverted microscope. The resulting deposits at higher solid content are imaged by scanning electron microscopy in or- der to relate the morphology and fine structure to the internal flows within the droplet. The evaporation of binary solvent mixtures can cause a gra- dient in the surface tension at the liquid-air interface, resulting in a Marangoni flow. The ratio of solvent composition and the surface tension of the more volatile solvent relative to the less volatile solvent is varied, to manipulate the direction and mag- nitude of any introduced Marangoni flow. Pure solvent droplets are compared to mixed binary solvent systems, to determine the importance of Marangoni flows on the morphology of the final deposit

Internal Flows and Particle Transport Inside Picoliter Droplets of Binary Solvent Mixtures

The flows in evaporating droplets of binary mixtures are much more complicated than single solvent systems. Solutal Marangoni flows are generated due to differential evaporation of components. High-speed imaging techniques are used to visualize how internal flows transport particles to build up the end deposit. Circulatory flow along streamlines develops inside droplets at the contact line or central region, depending on the direction of the Marangoni flow. Re-circulation of particles can reduce the build up of a ring stain. Additionally, particles migrate across streamlines to collect at the droplet center independent of where the circulating regions occur. Potential mechanisms for particle migration are discussed, including chemophoresis, thermophoresis and shear-induced migration

Mutational screening of splicing factor genes in cases with autosomal dominant retinitis pigmentosa.

PURPOSE: Mutations in genes encoding proteins from the tri-snRNP complex of the spliceosome account for more than 12% of cases of autosomal dominant retinitis pigmentosa (adRP). Although the exact mechanism by which splicing factor defects trigger photoreceptor death is not completely clear, their role in retinitis pigmentosa has been demonstrated by several genetic and functional studies. To test for possible novel associations between splicing factors and adRP, we screened four tri-snRNP splicing factor genes (EFTUD2, PRPF4, NHP2L1, and AAR2) as candidate disease genes. METHODS: We screened up to 303 patients with adRP from Europe and North America who did not carry known RP mutations. Exon-PCR and Sanger methods were used to sequence the NHP2L1 and AAR2 genes, while the sequences of EFTUD2 and PRPF4 were obtained by using long-range PCRs spanning coding and non-coding regions followed by next-generation sequencing. RESULTS: We detected novel missense changes in individual patients in the sequence of the genes PRPF4 and EFTUD2, but the role of these changes in relationship to disease could not be verified. In one other patient we identified a novel nucleotide substitution in the 5' untranslated region (UTR) of NHP2L1, which did not segregate with the disease in the family. CONCLUSIONS: The absence of clearly pathogenic mutations in the candidate genes screened in our cohort suggests that EFTUD2, PRPF4, NHP2L1, and AAR2 are either not involved in adRP or are associated with the disease in rare instances, at least as observed in this study in patients of European and North American origin

Next generation sequencing of pooled samples reveals new SNRNP200 mutations associated with retinitis pigmentosa.

The gene SNRNP200 is composed of 45 exons and encodes a protein essential for pre-mRNA splicing, the 200 kDa helicase hBrr2. Two mutations in SNRNP200 have recently been associated with autosomal dominant retinitis pigmentosa (adRP), a retinal degenerative disease, in two families from China. In this work we analyzed the entire 35-Kb SNRNP200 genomic region in a cohort of 96 unrelated North American patients with adRP. To complete this large-scale sequencing project, we performed ultra high-throughput sequencing of pooled, untagged PCR products. We then validated the detected DNA changes by Sanger sequencing of individual samples from this cohort and from an additional one of 95 patients. One of the two previously known mutations (p.S1087L) was identified in 3 patients, while 4 new missense changes (p.R681C, p.R681H, p.V683L, p.Y689C) affecting highly conserved codons were identified in 6 unrelated individuals, indicating that the prevalence of SNRNP200-associated adRP is relatively high. We also took advantage of this research to evaluate the pool-and-sequence method, especially with respect to the generation of false positive and negative results. We conclude that, although this strategy can be adopted for rapid discovery of new disease-associated variants, it still requires extensive validation to be used in routine DNA screenings. © 2011 Wiley-Liss, Inc

A homozygous missense mutation in the IRBP gene (RBP3) associated with autosomal recessive retinitis pigmentosa.

Item does not contain fulltextPURPOSE: Interphotoreceptor retinoid-binding protein (IRBP) has been considered essential for normal rod and cone function, as it mediates the transport of retinoids between the photoreceptors and the retinal pigment epithelium. This study was performed to determine whether mutations in the IRBP gene (RBP3) are associated with photoreceptor degeneration. METHODS: A consanguineous family was ascertained in which four children had autosomal recessive retinitis pigmentosa (RP). Homozygosity mapping performed with SNP microarrays revealed only one homozygous region shared by all four affected siblings. Sequencing of RBP3, contained in this region, was performed in this family and others with recessive RP. Screening was also performed on patients with various other forms of retinal degeneration or malfunction. RESULTS: Sequence analysis of RBP3 revealed a homozygous missense mutation (p.Asp1080Asn) in the four affected siblings. The mutation affects a residue that is completely conserved in all four homologous modules of the IRBP protein of vertebrate species and in C-terminal-processing proteases, photosynthesis enzymes found in bacteria, algae, and plants. Based on the previously reported crystal structure of Xenopus IRBP, the authors predict that the Asp1080-mediated conserved salt bridge that appears to participate in scaffolding of the retinol-binding domain is abolished by the mutation. No RBP3 mutations were detected in 395 unrelated patients with recessive or isolate RP or in 680 patients with other forms of hereditary retinal degeneration. CONCLUSIONS: Mutations in RBP3 are an infrequent cause of autosomal recessive RP. The mutation Asp1080Asn may alter the conformation of the IRBP protein by disrupting a conserved salt bridge