Ultrahigh Passive Cooling Power in Hydrogel with Rationally Designed Optofluidic Properties.

The cooling power of a radiative cooler is more than halved in the tropics, e.g., Singapore, because of its harsh weather conditions including high humidity (84% on average), strong downward atmospheric radiation (∼40% higher than elsewhere), abundant rainfall, and intense solar radiation (up to 1200 W/m2 with ∼58% higher UV irradiation). So far, there has been no report of daytime radiative cooling that well achieves effective subambient cooling. Herein, through integrated passive cooling strategies in a hydrogel with desirable optofluidic properties, we demonstrate stable subambient (4-8 °C) cooling even under the strongest solar radiation in Singapore. The integrated passive cooler achieves an ultrahigh cooling power of ∼350 W/m2, 6-10 times higher than a radiative cooler in a tropical climate. An in situ study of radiative cooling with various hydration levels and ambient humidity is conducted to understand the interaction between radiation and evaporative cooling. This work provides insights for the design of an integrated cooler for various climates.

The performance of homopolymer detection using dichromatic and tetrachromatic fluorogenic next-generation sequencing platforms.

OBJECTIVES: Homopolymer (HP) sequencing is error-prone in next-generation sequencing (NGS) assays, and may induce false insertion/deletions and substitutions. This study aimed to evaluate the performance of dichromatic and tetrachromatic fluorogenic NGS platforms when sequencing homopolymeric regions. RESULTS: A HP-containing plasmid was constructed and diluted to serial frequencies (3%, 10%, 30%, 60%) to determine the performance of an MGISEQ-2000, MGISEQ-200, and NextSeq 2000 in HP sequencing. An evident negative correlation was observed between the detected frequencies of four nucleotide HPs and the HP length. Significantly decreased rates (P < 0.01) were found in all 8-mer HPs in all three NGS systems at all four expected frequencies, except in the NextSeq 2000 at 3%. With the application of a unique molecular identifier (UMI) pipeline, there were no differences between the detected frequencies of any HPs and the expected frequencies, except for poly-G 8-mers using the MGI 200 platform. UMIs improved the performance of all three NGS platforms in HP sequencing. CONCLUSIONS: We first constructed an HP-containing plasmid based on an EGFR gene backbone to evaluate the performance of NGS platforms when sequencing homopolymeric regions. A highly comparable performance was observed between the MGISEQ-2000 and NextSeq 2000, and introducing UMIs is a promising approach to improve the performance of NGS platforms in sequencing homopolymeric regions.

Characterization and mitigation of artifacts derived from NGS library preparation due to structure-specific sequences in the human genome.

BACKGROUND: Hybridization capture-based targeted next generation sequencing (NGS) is gaining importance in routine cancer clinical practice. DNA library preparation is a fundamental step to produce high-quality sequencing data. Numerous unexpected, low variant allele frequency calls were observed in libraries using sonication fragmentation and enzymatic fragmentation. In this study, we investigated the characteristics of the artifact reads induced by sonication and enzymatic fragmentation. We also developed a bioinformatic algorithm to filter these sequencing errors. RESULTS: We used pairwise comparisons of somatic single nucleotide variants (SNVs) and insertions and deletions (indels) of the same tumor DNA samples prepared using both ultrasonic and enzymatic fragmentation protocols. Our analysis revealed that the number of artifact variants was significantly greater in the samples generated using enzymatic fragmentation than using sonication. Most of the artifacts derived from the sonication-treated libraries were chimeric artifact reads containing both cis- and trans-inverted repeat sequences of the genomic DNA. In contrast, chimeric artifact reads of endonuclease-treated libraries contained palindromic sequences with mismatched bases. Based on these distinctive features, we proposed a mechanistic hypothesis model, PDSM (pairing of partial single strands derived from a similar molecule), by which these sequencing errors derive from ultrasonication and enzymatic fragmentation library preparation. We developed a bioinformatic algorithm to generate a custom mutation "blacklist" in the BED region to reduce errors in downstream analyses. CONCLUSIONS: We first proposed a mechanistic hypothesis model (PDSM) of sequencing errors caused by specific structures of inverted repeat sequences and palindromic sequences in the natural genome. This new hypothesis predicts the existence of chimeric reads that could not be explained by previous models, and provides a new direction for further improving NGS analysis accuracy. A bioinformatic algorithm, ArtifactsFinder, was developed and used to reduce the sequencing errors in libraries produced using sonication and enzymatic fragmentation.

Irritable bowel syndrome in children: the placebo response rate and influencing factors a meta-analysis.

BACKGROUND: Irritable bowel syndrome is common in children and exhibits a high placebo response. This study was to explore the placebo response rate and its influencing factors in children with irritable bowel syndrome. METHODS: A systematic search was performed on Pubmed, Embase, MEDLINE, Cochrane Library, CNKI, Wanfang, and CBM from database inception to March 2022. Randomized controlled trials of irritable bowel syndrome in children were included in the study. The primary outcome was the placebo response rate of improvement. RESULTS: Thirteen studies were included, with 445 patients in the placebo group. The rate of improvement and abdominal pain disappearance were 28.2% (95% CI, 16.6-39.9%) and 5% (95% CI, 0-18.4%). The placebo response based on the abdominal pain score was 0.675 (95% CI, 0.203-1.147). The mode of administration (P < 0.01), dosing schedule (P < 0.01), and clinical outcome assessor (P = 0.04) have a significant impact on the magnitude of placebo effect. CONCLUSIONS: The placebo response rate for pediatric irritable bowel syndrome was 28.2%. In clinical trials, reducing dosing frequency, selecting appropriate dosage forms, and using patient-reported outcomes can help mitigate the placebo effect. IMPACT: This is the first meta-analysis to assess the placebo response rates for improvement and disappearance in children with IBS. The finding suggested that the mode of administration, dosing schedule, and clinical outcome assessor could potentially influence the magnitude of the placebo effect in children with IBS. This study would provide a basis for estimating sample size in clinical trial design with a placebo control.

Study on the therapeutic effect of sintilimab combined with modified DCF regimen on advanced gastric cancer and its impact on Th1/Th2 immune balance.

The aim of this study was to observe the therapeutic effect of sintilimab combined with a modified docetaxel + cisplatin + fluorouracil (DCF) regimen on advanced gastric cancer and its effect on Th1/Th2 immune balance. Ninety-eight cases of advanced gastric cancer patients who visited our hospital from April 2020 to May 2022 were selected and divided into 48 cases each in the conventional group and the research group by random number table method; the DCF regimen was adopted in the conventional group, and sintilimab combined with modified DCF regimen was adopted in the research group, and the therapeutic effects of the patients in the two groups and the changes of Th1/Th2 immune indexes were compared. CEA, CA199, CA242, CD168 AQ3, and IL-4 in the study group were lower than those in the conventional group at the end of three cycles of treatment, and the difference was statistically significant (P < 0.001). The levels of IFN-γ and IL-4 in the study group at the end of three cycles of treatment were higher than those in the conventional group (P < 0.001). The incidence of adverse reactions during treatment in the study group was lower than that in the conventional group (P < 0.001), and the grading of adverse reactions in the study group was milder than that in the conventional group. Sintilimab combined with a modified DCF regimen in the treatment of advanced gastric cancer not only improves the therapeutic effect but also positively affects the Th1/Th2 immune balance, which provides better immune regulation for patients with advanced gastric cancer.

A comprehensive performance evaluation, comparison, and integration of computational methods for detecting and estimating cross-contamination of human samples in cancer next-generation sequencing analysis.

Cross-sample contamination is one of the major issues in next-generation sequencing (NGS)-based molecular assays. This type of contamination, even at very low levels, can significantly impact the results of an analysis, especially in the detection of somatic alterations in tumor samples. Several contamination identification tools have been developed and implemented as a crucial quality-control step in the routine NGS bioinformatic pipeline. However, no study has been published to comprehensively and systematically investigate, evaluate, and compare these computational methods in the cancer NGS analysis. In this study, we comprehensively investigated nine state-of-the-art computational methods for detecting cross-sample contamination. To explore their application in cancer NGS analysis, we further compared the performance of five representative tools by qualitative and quantitative analyses using in silico and simulated experimental NGS data. The results showed that Conpair achieved the best performance for identifying contamination and predicting the level of contamination in solid tumors NGS analysis. Moreover, based on Conpair, we developed a Python script, Contamination Source Predictor (ConSPr), to identify the source of contamination. We anticipate that this comprehensive survey and the proposed tool for predicting the source of contamination will assist researchers in selecting appropriate cross-contamination detection tools in cancer NGS analysis and inspire the development of computational methods for detecting sample cross-contamination and identifying its source in the future.

Hierarchically Patterned Self-Cleaning Polymer Composites for Daytime Radiative Cooling.

Passive daytime radiative cooling (PDRC) has the potential to reduce energy demand and mitigate global warming. However, surface contamination from dust and bacterial buildup limits practical PDRC applications. Here, we develop a hierarchically patterned nanoporous composite (HPNC) using a facile template-molding fabrication method to integrate PDRC materials with self-cleaning and antibacterial functions. The HPNC design decouples multifunctional control into different characteristic length scales that can be optimized simultaneously. The nanoporous polymer matrix embedded with tunable fillers enables 7.8 and 4.4 °C temperature reduction for outdoor personal and building cooling, respectively, under intense solar irradiance. Meanwhile, a microscale pillar array pattern integrated into the HPNC enables superhydrophobicity with self-cleaning and antisoiling functions to mitigate surface contamination. Moreover, the surface coating of photocatalytic agents can generate photoinduced antibacterial effects. The scalable fabrication and multifunctional capabilities of our HPNC design offer a promising solution for practical PDRC applications with minimal maintenance needs.

Defect Engineering of WO3 by Rapid Flame Reduction for Efficient Photoelectrochemical Conversion of Methane into Liquid Oxygenates.

Photoelectrochemical (PEC) conversion is a promising way to use methane (CH4) as a chemical building block without harsh conditions. However, the PEC conversion of CH4 to value-added chemicals remains challenging due to the thermodynamically favorable overoxidation of CH4. Here, we report WO3 nanotube (NT) photoelectrocatalysts for PEC CH4 conversion with high liquid product selectivity through defect engineering. By tuning the flame reduction treatment, we carefully controlled the oxygen vacancies of WO3 NTs. The optimally reduced WO3 NTs suppressed overoxidation of CH4 showing a high total C1 liquid selectivity of 69.4% and a production rate of 0.174 µmol cm-2 h-1. Scanning electrochemical microscopy revealed that oxygen vacancies can restrain the production of hydroxyl radicals, which, in excess, could further oxidize C1 intermediates to CO2. Additionally, band diagram analysis and computational studies elucidated that oxygen vacancies thermodynamically suppress overoxidation. This work introduces a strategy for understanding and controlling the selectivity of photoelectrocatalysts for direct conversion of CH4 to liquids.

Comparison of different ratios of cefoperazone/sulbactam in patients with pyelonephritis.

Objective: To compare the clinical efficacy of different ratios of cefoperazone/sulbactam in the treatment of patients with pyelonephritis. Methods: In this retrospective study clinical records of patients with pyelonephritis treated in Huzhou Traditional Chinese Medicine Hospital from July 2020 to July 2021 were collected,. It included 55 patients who received cefoperazone/sulbactam 2:1 treatment (Control group) and 57 patients who received 1 cefoperazone/sulbactam 1:1 treatment (Observation group). Clinical response, inflammatory reaction and bacterial clearance were compared between the two groups. Results: The levels of C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-8 (IL-8) and leukocyte count (WBC) in the observation group were lower than those in the control group (P<0.05). The total efficacy of the Observation-group was 92.98%, higher than 80.00% of the control group (P<0.05). Fifty-eight strains of bacteria were isolated from the Control-group and 59 strains from the Observation-group. The bacterial clearance rates were 65.52% (38/58) and 83.05% (49/59), respectively. The differences were statistically significant (P<0.05). Conclusions: The clinical efficacy of 1:1 ratio of cefoperazone/sulbactam in the treatment of patients with pyelonephritis was superior that of 2:1 ratio. This ratio allows to fully utilize the antibacterial effect of cefoperazone, with a significant decrease in inflammation markers and an improvement in bacterial clearance.

Epidemiological study of HPV infection in 40,693 women in Putian: a population study based on screening for high-risk HPV infection.

BACKGROUND: The infection rate of human papillomavirus (HPV) is high in the coastal regions of China. However, the infection rate among high-risk genotypes of women in Putian City is unknown. Therefore, this study aimed to analyse the epidemiology of high-risk HPV infection among women in Putian and provide a reference for the diagnosis, treatment and vaccination of cervical cancer in this region. METHODS: The data used were obtained from the Chinese government's public health program ("Cervical and Breast Cancer Screening Project"). A total of 40,693 female cervical cell exfoliation samples screened for high-risk HPV at the Affiliated Hospital of Putian University from July 2020 to December 2021 were enrolled. DNA was extracted using a fully automatic extractor. Then, 14 high-risk genotypes of HPV were detected by polymerase chain reaction. The characteristics of HPV infection, distribution of high-risk genotypes, infection types and thinprep cytologic test (TCT) classification at different age groups were analysed. RESULTS: Among the 40,693 samples, 3899 were infected with HPV, with an infection rate of 9.6%. Accordingly, HPV infection rates gradually increased with age, and statistically significant differences were observed among age groups (χ2 = 74.03, P < 0.01). The infection rates of high-risk HPV52, HPV58 and HPV16 were in the top three and increased with age. Single infection was dominant (84.7%), followed by double infections (12.7%). The cervical cytology of 3899 HPV-positive people can be classified into negative for intraepithelial lesion and malignancy (NILM, 88.0%), atypical squamous cells of undetermined significance (ASC-US, 6.6%), atypical squamous cells-cannot exclude high-grade squamous intraepithelial lesion (ASC-H, 1.4%), low-grade squamous intraepithelial lesion (LSIL, 3.2%) and high-grade squamous intraepithelial lesion (HSIL, 0.8%). HPV16 infection rate increased with increasing severity of cervical cytology (χ2trend = 43.64, P < 0.01), whereas the infection rates of HPV52 (χ2trend = 13.89, P < 0.01) and HPV58 (χ2trend = 13.50, P < 0.01) showed opposite trends. CONCLUSION: The infection rate of female HPV high-risk screening in this region was 9.6% and mainly involved single infections. In addition, HPV16, HPV52 and HPV58 were closely related to the severity of cervical cytology. Effective screening, vaccination and education are needed. The 9-valent vaccine will be effective in reducing cervical pre-invasive disease. It would also be reasonable to state that the rising trend in HPV infection and high grade cytology with age emphasises the need to target older women with screening. Vaccination of younger women (aged ≤ 25) will lay the foundation for better cancer outcomes in the future.

Neuron secrete exosomes containing miR-9-5p to promote polarization of M1 microglia in depression.

BACKGROUND: Neuroinflammation is an important component mechanism in the development of depression. Exosomal transfer of MDD-associated microRNAs (miRNAs) from neurons to microglia might exacerbate neuronal cell inflammatory injury. RESULTS: By sequence identification, we found significantly higher miR-9-5p expression levels in serum exosomes from MDD patients than healthy control (HC) subjects. Then, in cultured cell model, we observed that BV2 microglial cells internalized PC12 neuron cell-derived exosomes while successfully transferring miR-9-5p. MiR-9-5p promoted M1 polarization in microglia and led to over releasing of proinflammatory cytokines, such as interleukin-1ß (IL-1ß), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), which exacerbated neurological damage. Furthermore, we identified suppressor of cytokine signaling 2 (SOCS2) as a direct target of miR-9-5p. Overexpression of miR-9-5p suppressed SOCS2 expression and reactivated SOCS2-repressed Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) pathways. Consistently, we confirmed that adeno-associated virus (AAV)-mediated overexpression of miR-9-5p polarized microglia toward the M1 phenotype and exacerbated depressive symptoms in chronic unpredictable mild stress (CUMS) mouse mode. CONCLUSION: MiR-9-5p was transferred from neurons to microglia in an exosomal way, leading to M1 polarization of microglia and further neuronal injury. The expression and secretion of miR-9-5p might be novel therapeutic targets for MDD.

Three-Dimensional Printable Nanoporous Polymer Matrix Composites for Daytime Radiative Cooling.

Daytime radiative cooling presents an exciting new strategy for combating global warming, because it can passively cool buildings by reflecting sunlight and utilizing the infrared atmospheric window to eject heat into outer space. Recent progress with novel material designs showed promising subambient cooling performance under direct sunlight. However, large-scale implementation of radiative cooling technologies is still limited by the high-cost and complex fabrication. Here, we develop a nanoporous polymer matrix composite (PMC) to enable rapid production and cost reduction using commercially available polymer processing techniques, such as molding, extrusion, and 3D printing. With a high solar reflectance of 96.2% and infrared emissivity > 90%, the nanoporous PMC achieved a subambient temperature drop of 6.1 °C and cooling power of 85 W/m2 under direct sunlight, which are comparable to the state-of-the-art. This work offers great promise to make radiative cooling technologies more viable for saving energy and reducing emissions in building cooling applications.

Analysis of the improvement of serological indexes in patients with diabetic nephropathy and hypertension using Valsartan combined with Nifedipine controlled-release regimen.

Objective: To investigate the effect of valsartan combined with nifedipine controlled-release Tablets on diabetic nephropathy (DN) patients with hypertension. Methods: The clinical records of 80 DN patients with hypertension registered in our hospital from April 2020 to April 2021 were collected. The records showed that 38 patients were treated with oral nifedipine controlled-release tablets (control group) and 42 - with oral valsartan combined with nifedipine controlled-release tablets (observation group). The improvement of serological indexes after treatment was compared and analyzed between the two groups. Results: After treatment, the levels of fasting blood glucose (FBG), systolic and diastolic blood pressure, bone oligomeric matrix protein (COMP), thrombin regulatory protein (TM) and Microalbumin (mALB) in the observation group were lower than those in the control group (P<0.05), while the level of angiopoietin-1 (Ang-1) was higher than those in the control group (P<0.05). After the treatment, the levels of homocysteine (Hcy), Cystatin C (CysC) and transforming growth factor ß1(TGF-ß1) in the observation group were lower than those in the control group (P<0.05). The levels of adiponectin (APN), aldosterone (ALD) and gastric growth promoting factor (ghrelin) in the observation group after the treatment were lower than those in the control group (P<0.05). Conclusions: A combination of valsartan and nifedipine controlled-release tablets in DN patients with hypertension can effectively control blood glucose and blood pressure, improve the serological indexes such as COMP, TM, mAlb, Ang-1, Hcy, CysC, TGF-ß1, APN, ALD and ghrelin, and potentially reduce and delay renal function damage.

Polypseudorotaxanes Derived from Tetraphenylethylene: Preparation and Tandem-Activated Aggregation-Induced Emission.

Tuning the fluorescence of aggregation-induced emission (AIE)-based materials in a reversible way is essential and a requisite for their applications. The multiple host-guest interactions of polypseudorotaxanes (PPRs) could alter the aggregation state of hydrophobic AIE-based polymeric materials and consequently switch the fluorescence. Herein, tetraphenylethylene (TPE) as a typical AIE molecule has been incorporated into the main chains of the guest polyurethane via a step condensation between poly(ethylene glycol) (PEG)-based dicarbonate and TPE-diamine along with the cleavable disulfide bonds. γ-Cyclodextrins (γ-CDs) can selectively recognize the TPE units at the polyurethane chains to afford a PPR. Hydrophilic PEG segments and γ-CD molecules in the PPR could promote the disaggregation of TPE units, suppressing the fluorescence emission of TPE. To restore the aggregated state and fluorescence of TPE units, tris(2-carboxyethyl)phosphine (TCEP) and α-amylase are sequentially introduced to cleave the disulfide bonds and cut α-1,4 glycosidic bonds of γ-CD, reactivating the AIE behavior of PPR tandemly and accomplishing the reversible cycle of tuning the fluorescence of TPE. The present study provides a tandem way to switch the AIE behavior of polymeric materials reversibly.

Internal states and extrinsic factors both determine monkey vocal production.

A key question for understanding speech evolution is whether or not the vocalizations of our closest living relatives-nonhuman primates-represent the precursors to speech. Some believe that primate vocalizations are not volitional but are instead inextricably linked to internal states like arousal and thus bear little resemblance to human speech. Others disagree and believe that since many primates can use their vocalizations strategically, this demonstrates a degree of voluntary vocal control. In the current study, we present a behavioral paradigm that reliably elicits different types of affiliative vocalizations from marmoset monkeys while measuring their heart rate fluctuations using noninvasive electromyography. By modulating both the physical distance between marmosets and the sensory information available to them, we find that arousal levels are linked, but not inextricably, to vocal production. Different arousal levels are, generally, associated with changes in vocal acoustics and the drive to produce different call types. However, in contexts where marmosets are interacting, the production of these different call types is also affected by extrinsic factors such as the timing of a conspecific's vocalization. These findings suggest that variability in vocal output as a function of context might reflect trade-offs between the drive to perpetuate vocal contact and conserving energy.

Public attention about COVID-19 on social media: An investigation based on data mining and text analysis.

The COVID-19 epidemic is influencing global population. Social media has become important platforms to acquire and exchange information during the outbreak of COVID-19. This study explores public attention on social media. Popular Weibo texts related to COVID-19 with "coronavirus" and "pneumonia" as the keywords during December 27, 2019 and May 31, 2020 were collected in our study for public attention analysis. By combining data mining and text analysis, the public attention level trend in different stages were presented. Then a correlation analysis between public attention level and COVID-19 related cases number, topic analysis, and sentiment analysis were conducted. Significant positive correlation between public attention level and COVID-19 related cases number was identified. Based on Latent Dirichlet Allocation model, topic extraction was implemented in different stages and 41 topics were identified totally. For a comprehensive understanding of public emotions, sentiment analysis was performed. This study provides valuable lessons for public response to COVID-19.

Neddylation inhibition activates the protective autophagy through NF-κB-catalase-ATF3 Axis in human esophageal cancer cells.

BACKGROUND: Protein neddylation plays a tumor-promoting role in esophageal cancer. Our previous study demonstrated that neddylation inhibition induced the accumulation of ATF4 to promote apoptosis in esophageal cancer cells. However, it is completely unknown whether neddylation inhibition could induce autophagy in esophageal cancer cells and affect the expression of other members of ATF/CREB subfamily, such as ATF3. METHODS: The expression of relevant proteins of NF-κB/Catalase/ATF3 pathway after neddylation inhibition was determined by immunoblotting analysis and downregulated by siRNA silencing for mechanistic studies. ROS generation upon MLN4924 treatment was determined by H2-DCFDA staining. The proliferation inhibition induced by MLN4924 was evaluated by ATPLite assay and apoptosis was evaluated by Annexin V /PI double staining. RESULTS: For the first time, we reported that MLN4924, a specific inhibitor of Nedd8-activating enzyme, promoted the expression of ATF3 to induce autophagy in esophageal cancer. Mechanistically, MLN4924 inhibited the activity of CRLs and induced the accumulation of its substrate IκBα to block NF-κB activation and Catalase expression. As a result, MLN4924 activated ATF3-induced protective autophagy, thereby inhibiting MLN4924-induced apoptosis, which could be alleviated by ATF3 silencing. CONCLUSIONS: In our study, we elucidates a novel mechanism of NF-κB/Catalase/ATF3 pathway in MLN4924-induced protective autophagy in esophageal cancer cells, which provides a sound rationale and molecular basis for combinational anti-ESCC therapy with knockdown ATF3 and neddylation inhibitor (e.g. MLN4924). Video abstract.

Ascorbate inducible N259 glycans on prolyl 4-hydroxylase subunit α1 promote hydroxylation and secretion of type I collagen.

Ascorbic acid (vitamin C, VC) increases the secretion of mature collagen by promoting the activity of prolyl 4-hydroxylase subunit α 1 (P4HA1). To explore the mechanism involved, we investigated the role of N-linked glycosylation, which can regulate enzyme activity. P4HA1 has two glycosylation sites, Asn (N) 113 and N259. Our studies show that glycosylation of N259, but not N113, by STT3B and magnesium transporter 1 (MAGT1) is augmented by VC. N259 glycosylation on P4HA1 correlates with enhanced pepsin-resistant collagen 1α2 secretion. Downregulation of Stt3b and Magt1 reduces N259 glycans on P4HA1. In collagen 1α2 purified from Stt3b-silenced fibroblasts, decreased hydroxylation is found at five specific proline residues, while significantly increased hydroxylation is noted at two proline residues. Similarly, in collagen 1α1, reduced proline hydroxylation is detected at eight sites and increased proline hydroxylation is found at four sites. These results suggest that N-linked glycosylation of P4HA1 can direct hydroxylation at specific proline residues and affect collagen maturation.

Prion dimer is heterogenous and is modulated by multiple negative and positive motifs.

The conversion of the normal prion protein (PrP) into a scrapie prion (PrPSc) is incompletely understood. Theoretically, the smallest PrP aggregate is a dimer. Human PrP contains two cysteines at positions 179 (C179) and 214 (C214) enabling disulfide bonding. Here, we report that our recombinant human PrP (r-hPrP) preparations contain 0.2-0.8% dimer, which is linked by either one or two disulfide bonds, connected by C179-C179, C214-C214, or C179-C214. Furthermore, dimerization is regulated by multiple motifs. While residues 36-42 inhibit, residues 90-125, and 195-212 promote dimerization. Mutating individual residue between 36 and 42 enhances dimerization whereas mutating the positively charged residues within 95-115, or the negatively charged residues within 195-212 prevent dimerization. Although deletion of the entire octapeptide-repeat (5OR) region prevents dimerization, mutating the histidines within the 5OR enhances dimerization. In addition, we found that two out of three brain lysates from patients with inherited prion disease had more PrP dimers than controls. Thus, PrP dimerization may contribute to prion diseases.