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There are two general types of ion exchange resins: those that exchange positive ions, called cation exchange resins, and those that exchange negative ions, called anion exchange resins. A cation is an ion with a positive charge. Common cations include Ca+2, Mg+2, Fe+2, and H+1. A cation resin is one that exchanges positive ions. An anion is an ion with a negative charge. Common anions include Cl-1, SO4-2, and OH-1 . An anion resin is one that exchanges negative ions. Chemically, both types are similar and belong to a group of compounds called polymers, which are extremely large molecules that are formed by the combination of many molecules of one or two compounds in a repeating structure that produces long chains. A demineralizer is a vessel, usually with a volume of several cubic feet, that contains the resin.


A demineralizer may contain an intimate mixture of both cation exchange resins and anion exchange resins and is called a mixed bed. Two-bed demineralizers have two vessels, the first containing cation resin followed by a separate vessel containing anion resin. Physically, ion exchange resins are formed in the shape of very small beads, called resin beads, with an average diameter of about 0.5 millimeters. Wet resin has the appearance of damp, transparent, amber sand and is insoluble in water, acids, and bases. The ratio is normally 2 parts cation resin to 3 parts anion resin.

The ion exchange resin is contained in a vessel with a volume of several cubic feet. Retention elements at the top and bottom consist of screens, slotted cylinders, or other suitable devices with openings smaller than the resin beads to prevent the resin from escaping from the vessel. When the resin bed is a uniform mixture of cation and anion resins in a volume (typically in a ratio of 2 parts cation resin to 3 parts anion resin). This arrangement is called a mixed-bed resin, as opposed to an arrangement of cation and anion resins in discrete layers or separate vessels.

The use of different volumes of the two types of resins is due to the difference in exchange capacity between cation and anion resins. Exchange capacity is the amount of impurity that a given amount of resin can remove, and it has units of moles/ml, equivalents/ml, or moles/gm. The anion resin is less dense than the cation resin; thus, it has a smaller exchange capacity, and a larger volume is needed for anion resins than for the cation resins to obtain equal total exchange capabilities.

Lentivirus is one of the most efficient gene transfer vectors for integrating a gene of interest into the target cell DNA. The purification of lentiviral vectors is challenging due to the low stability of this enveloped virus that is sensitive to low pH, high salt, temperature, and shear forces. Typically, lentivirus purification is carried out using anion exchange capture chromatography, but with low recoveries. Here, weak anion exchange capture is identified as a method for improved lentivirus recovery using the CaptoTM DEAE resin.

In addition to the aforementioned Glu90, most CCRs contain four other Glu residues in the 2nd helix and the loop between helices 2 and 3 (Glu82, Glu83, Glu90, Glu97 and Glu101 in CrChR2). It has been proposed that the absence of Glu residues in the positions corresponding to Glu83, Glu97 and Glu101 contributes to the formation of an anion-conducting pore in natural ACRs10. Indeed, in nearly all confirmed natural ACRs non-carboxylic residues are found in these three positions (Supplementary Fig. S1). However in the highly conductive ZipACR (Fig. 2), Glu101 is conserved (Supplementary Fig. S1), which demonstrates that the presence of a non-carboxylate residue at least in this position is not absolutely necessary for anion conductance.

Here we present the results of screening ACR homologs identified in high-throughput plant/protist transcriptome sequencing projects17,18. We found that all transcripts that generated photocurrents upon expression in mammalian cells acted as light-gated anion channels. This result confirmed that cation or anion selectivity of channelrhodopsins can be accurately predicted from the protein sequence information or, in other words, that ACRs and CCRs form two structurally and functionally distinct protein families. When only three natural ACRs were known, testable prediction of structural determinants of their anion conductance was difficult. The new expanded set of 20 functional sequences will serve as a better guide towards this goal.

Our expansion of the family of natural ACRs to include 20 functional members provides the foundation for further deciphering anion conductance mechanisms of these proteins and for their molecular engineering to better suit the needs of inhibitory optogenetics.

Trupanion pet insurance ties for No. 3 in our Best Pet Insurance Companies of 2023 ratings. It offers comprehensive dog and cat insurance covering accidents, illnesses, injuries, and medical conditions, including breed-specific conditions. Founded in 2000, Trupanion acquired American Pet Insurance Company in 2007, which underwrites its insurance policies. Aside from its dog and cat policies, Trupanion sells Recovery and Complementary Care, which covers certain treatments, like behavioral modification, chiropractic, and acupuncture.

Trupanion offers accident and illness coverage for cats and dogs, with options to add coverage for rehab and alternative therapies, pet owners assistance, or pets who are breeders. Its policies have no coverage limits, and you have a broad range of deductible options to choose from.

Trupanion offers a medical pet insurance plan for cats and dogs. It covers hospitalization and surgery, emergency visits, hereditary and congenital conditions, diagnoses, prescription medications, and breed-specific conditions, like hip dysplasia and heart disease. Pet owners can purchase additional Recovery and Complementary Care coverage for alternative treatments, like acupuncture, chiropractic, and behavioral modification.

You can choose a $0 to $1,000 lifetime per condition deductible, so you only pay the deductible when your pet develops a new condition vs. paying the deductible every year. Once you reach your deductible, Trupanion pays for 90% of covered medical conditions and veterinarian care as outlined in the policy.

Trupanion pet insurance for a cat (a under one-year-old male domestic shorthair) costs $30.88 per month for a $500 deductible. Trupanion dog insurance costs $70.12 per month for a $500 deductible for a one-year-old female mixed-breed dog weighing between 50 and 90 pounds. Exact pricing depends on the breed, your location, deductible, and pre-existing medical conditions.

Trupanion insurance has a lifetime per condition deductible, so after reaching the deductible for the first time, you only pay it when your pet is diagnosed with a new covered condition. The pet insurance plan has no payout limits. Trupanion has a vet direct pay option for participating veterinarian hospitals that immediately files your claim upon checkout at the vet so you pay your 10% portion (after meeting the deductible) and Trupanion pays the vet directly.

You can submit your claims for both Trupanion and Lemonade through a company app or website, but with Trupanion if the vet has its payment software the vet could submit the claim and be paid by Trupanion before you leave.

Trupanion has a waiting period of five days for injuries and 30 days for illnesses from the time you enroll in a pet insurance plan. After that, all listed medical injuries, illnesses, accidents, and vet care is covered. If your pet gets sick during the waiting period, Trupanion considers it a pre-existing condition that will not be included in the coverage.

Trupanion does not offer a wellness plan to cover vet exams, vaccinations, and other preventive care like dental cleaning. However, you can add on Recovery and Complementary Care for services including hydrotherapy, rehabilitative therapy, acupuncture, chiropractic, and behavioral modification.

Contact Trupanion customer support 24/7 by calling their toll-free customer service number, using its chatbot, or sending an email. You can also fill out an online form and Trupanion will get in touch with you.

To cancel a Trupanion pet insurance plan, provide written notice to customer service by email or regular mail at any time. If you cancel within the first 30 days of your policy and Trupanion has not paid you a claim, it will refund 100% of the premium and any enrollment fees.

When cells swell in hypo-osmotic solutions, chloride-selective ion channels (Cl(swell)) activate to reduce intracellular osmolality and prevent catastrophic cell rupture. Despite intensive efforts to assign a molecular identity to the mammalian Cl(swell) channel, it remains unknown. In an unbiased genome-wide RNA interference (RNAi) screen of Drosophila cells stably expressing an anion-sensitive fluorescent indicator, we identify Bestrophin 1 (dBest1) as the Drosophila Cl(swell) channel. Of the 23 screen hits with mammalian homologs and predicted transmembrane domains, only RNAi specifically targeting dBest1 eliminated the Cl(swell) current (I(Clswell)). We further demonstrate the essential contribution of dBest1 to Drosophila I(Clswell) with the introduction of a human Bestrophin disease-associated mutation (W94C). Overexpression of the W94C construct in Drosophila cells significantly reduced the endogenous I(Clswell). We confirm that exogenous expression of dBest1 alone in human embryonic kidney (HEK293) cells creates a clearly identifiable Drosophila-like I(Clswell). In contrast, activation of mouse Bestrophin 2 (mBest2), the closest mammalian ortholog of dBest1, is swell-insensitive. The first 64 residues of dBest1 conferred swell activation to mBest2. The chimera, however, maintains mBest2-like pore properties, strongly indicating that the Bestrophin protein forms the Cl(swell) channel itself rather than functioning as an essential auxiliary subunit. dBest1 is an anion channel clearly responsive to swell; this activation depends upon its N-terminus. 041b061a72

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