diff --git a/src/apps/rednatco/filtering.ts b/src/apps/rednatco/filtering.ts
new file mode 100644
index 0000000000000000000000000000000000000000..141e30efa44061f1539e30fbaf9d52463bf16332
--- /dev/null
+++ b/src/apps/rednatco/filtering.ts
@@ -0,0 +1,89 @@
+import { Expression } from '../../mol-script/language/expression';
+import { MolScriptBuilder as MSB } from '../../mol-script/language/builder';
+import { formatMolScript } from '../../mol-script/language/expression-formatter';
+
+export namespace Filtering {
+    export type FilterKind = 'empty'|'slices';
+
+    export type EmptyFilter = {
+        kind: 'empty',
+    };
+    export function EmptyFilter(): EmptyFilter {
+        return { kind: 'empty' };
+    }
+
+    export type SlicesFilter = {
+        kind: 'slices',
+        slices: {
+            chain: string;
+            residues?: number[];
+            altIds?: string[];
+        }[];
+    };
+    export function SlicesFilter(slices: SlicesFilter['slices']): SlicesFilter {
+        return { kind: 'slices', slices };
+    }
+
+    export type Filter = EmptyFilter|SlicesFilter;
+
+    function empty() {
+        return MSB.struct.generator.all();
+    }
+
+    function sliceExpr(slice: SlicesFilter['slices'][0]) {
+        let expr = MSB.core.rel.eq([MSB.struct.atomProperty.macromolecular.label_asym_id(), slice.chain]);
+
+        if (slice.residues && slice.residues.length > 0) {
+            let _expr = MSB.core.rel.eq([MSB.struct.atomProperty.macromolecular.label_seq_id(), slice.residues[0]]);
+            for (let idx = 1; idx < slice.residues.length; idx++) {
+                _expr = MSB.core.logic.or([
+                    _expr,
+                    MSB.core.rel.eq([MSB.struct.atomProperty.macromolecular.label_seq_id(), slice.residues[idx]])
+                ]);
+            }
+            expr = MSB.core.logic.and([expr, _expr]);
+        }
+
+        if (slice.altIds && slice.altIds.length > 0) {
+            let _expr = MSB.core.rel.eq([MSB.struct.atomProperty.macromolecular.label_alt_id(), slice.altIds[0]]);
+            for (let idx = 1; idx < slice.altIds.length; idx++) {
+                _expr = MSB.core.logic.or([
+                    _expr,
+                    MSB.core.rel.eq([MSB.struct.atomProperty.macromolecular.label_alt_id(), slice.altIds[idx]])
+                ]);
+            }
+
+            expr = MSB.core.logic.and([expr, _expr]);
+        }
+
+        return expr;
+    }
+
+    function slices(slices: SlicesFilter['slices']) {
+        if (slices.length > 0) {
+            let expr = sliceExpr(slices[0]);
+
+            for (let idx = 1; idx < slices.length; idx++) {
+                expr = MSB.core.logic.or([
+                    expr,
+                    sliceExpr(slices[idx])
+                ]);
+            }
+
+            expr = MSB.struct.generator.atomGroups({ 'atom-test': expr, 'group-by': MSB.struct.atomProperty.macromolecular.label_asym_id() });
+            console.log(formatMolScript(expr));
+
+            return expr;
+        }
+        return MSB.struct.generator.all();
+    }
+
+    export function toExpression(filter: Filter): Expression {
+        switch (filter.kind) {
+            case 'empty':
+                return empty();
+            case 'slices':
+                return slices(filter.slices);
+        }
+    }
+}